¶1
A class comprised of 69 installation and service technicians (Technicians) filed an action against employer Brink’s Home Security, Inc. (Brink’s). Technicians alleged that Brink’s violated the Washington Minimum Wage Act (MWA), chapter 49.46 RCW, by failing to compensate Technicians for time they spent driving company trucks from their homes to the first jobsite and back from the last jobsite (drive time). On summary judgment, the trial court held that Brink’s was liable for the drive time claim. Brink’s argues that the trial court erred in granting summary judgment on the drive time claim and in granting prejudgment interest, attorney fees, and costs. Brink’s also challenges the rate at which the trial court assessed prejudgment and postjudgment interest. We affirm the trial court.
*45FACTS
¶2 This case arises from Technicians’ employment with Brink’s in the Puget Sound area between November 1999 and July 2005. Technicians installed and serviced home security systems. Brink’s supplied Technicians with pickup trucks bearing the Brink’s logo and configured to carry the necessary tools and equipment.
¶3 Brink’s compensated all Technicians for the time spent driving the Brink’s trucks between jobsites. For the time spent driving to the first jobsite and from the last jobsite, Brink’s offered Technicians a choice between two programs. Under the first option, Technicians could drive their personal vehicles from their homes to the Brink’s office in Kent and pick up the Brink’s trucks at the Kent office. Under this option, Brink’s paid Technicians for the time spent driving the Brink’s trucks from the Kent office to the first jobsite and from the last jobsite to the Kent office. Brink’s did not pay them for the time spent commuting between their homes and the Kent office.
¶4 The second option — the subject of this litigation— allowed Technicians to keep the Brink’s trucks at their homes and drive them directly to and from the first and last jobsites without stopping at the Kent office. Brink’s named this option the home dispatch program (HDP). Technicians participating in the HDP received their daily job assignments through voice mail or handheld computers. Brink’s generally compensated Technicians in the HDP for any drive time in excess of 45 minutes from Technicians’ homes. Between September 2002 and January 2005, Brink’s implemented an interim HDP policy, wherein Brink’s paid Technicians for drive time to the first jobsite and from the last jobsite only if the site was located more than 45 minutes from the Technicians’ homes and the Brink’s office in Kent. If the particular drive qualified for compensation under this policy, Brink’s paid Technicians only for drive time in excess of 45 minutes.
*46¶5 In November 2002, Technicians filed a class action in Ring County Superior Court. Technicians alleged in part that Brink’s violated the MWA by failing to compensate Technicians for all drive time under the HDP. In September 2005, the trial court granted in part Technicians’ motion for partial summary judgment, ruling that Brink’s was liable for the drive time claim. Specifically, the trial court held that the time Technicians spent driving from home to the first jobsite and from the last jobsite back to their homes in company-issued trucks was work time under the MWA.
¶6 In January 2006, the trial court granted Technicians’ second motion for partial summary judgment, concluding that the class members were entitled to prejudgment interest and any back pay damages awarded in the case. At trial, the jury awarded Technicians back pay damages for the drive time claims. The court awarded prejudgment and postjudgment interest at the rate of 12 percent per annum and also awarded attorney fees and costs. Brink’s appealed and we granted Brink’s’ motion to transfer the case from Division One of the Court of Appeals.
ISSUES
¶7 A. Did the trial court err in holding that Brink’s violated the MWA by failing to compensate for drive time?
¶8 B. Did the trial court err in awarding prejudgment interest?
¶9 C. Did the trial court err in fixing the prejudgment and postjudgment interest rate at 12 percent?
¶10 D. Are Technicians entitled to attorney fees and costs?
ANALYSIS
¶11 Standard of Review. On review of summary judgment, we engage in the same inquiry as the trial court and view the facts and all reasonable inferences in the light *47most favorable to the nonmoving party. Fairbanks v. J.B. McLoughlin Co., 131 Wn.2d 96, 101, 929 P.2d 433 (1997). “Summary judgment is appropriate when there are no genuine issues of material fact and the moving party is entitled to judgment as a matter of law.” Cerrillo v. Esparza, 158 Wn.2d 194, 200, 142 P.3d 155 (2006); accord CR 56(c).
A. Drive Time Compensation
¶12 Under the MWA, employees are entitled to compensation for regular hours worked and for any overtime hours worked. See RCW 49.46.020, .130; see also Bostain v. Food Express, Inc., 159 Wn.2d 700, 708-09, 153 P.3d 846 (2007) (“Subject to specific exemptions, the MWA requires employers to pay their employees . . . overtime pay for the hours they work over 40 hours per week.”). This case requires us to determine whether Technicians’ drive time constitutes hours worked within the meaning of the MWA.
f 13 The legislature has not defined hours worked or addressed the compensability of employee travel time. Accordingly, WAC 296-126-002(8) governs the determination of whether drive time is compensable.1 Under WAC 296-126-002(8), “ ‘[hjours worked’ . . . mean[s] all hours during which the employee is authorized or required ... to be on duty on the employer’s premises or at a prescribed work place.” “[WJhere a regulation is clear and unambiguous, words . . . are given their plain and ordinary meaning unless a contrary intent appears.” Silverstreak, Inc. v. Dep’t of Labor & Indus., 159 Wn.2d 868, 881,154 P.3d 891 (2007). Thus, to determine whether drive time is compensable, we must examine the undisputed facts and assess whether Technicians are “on duty” at the “employer’s premises” or “prescribed work place” within the meaning of WAC 296--126-002(8).
*48¶14 In Anderson v. Department of Social & Health Services, 115 Wn. App. 452, 63 P.3d 134, review denied, 149 Wn.2d 1036 (2003), the Court of Appeals evaluated whether employee travel time was compensable under WAC 296--126-002(8). Id. at 456. Under the WAC standard, the court held that state employees who worked at the Special Commitment Center on McNeil Island were not entitled to compensation for time they spent traveling to work on the state/employer-provided ferry. Id. The employees were not “on duty” within the meaning of WAC 296-126-002(8) because “[d]uring passage, plaintiffs engage in various personal activities, such as reading, conversing, knitting, playing cards, playing hand-held video games, listening to CD (compact disc) players and radios, and napping. They perform no work during the passage.” Id. at 454. The court also concluded that the employees were not on the Special Commitment Center’s “ ‘premises’ ” or “ ‘prescribed work place’ ” during their commute for purposes of WAC 296-126--002(8). Id. at 456.
¶15 As in Anderson, we must evaluate the extent to which Brink’s restricts Technicians’ personal activities and controls Technicians’ time to determine whether Technicians are “on duty” for purposes of WAC 296-126-002(8). Here, Brink’s company policy strictly controls Technicians’ use of the Brink’s trucks, specifically mandating that they use the trucks “for company business only.” Clerk’s Papers (CP) at 74. To that end, Technicians may not carry non-Brink’s employees as passengers in the trucks. Id. Company policy also requires Technicians to wear seat belts, obey traffic laws, not park haphazardly, lock the vehicle at all times, and never carry alcohol. Id. Unlike ordinary commuters who regularly run errands during their commutes and carry additional passengers, Brink’s policy prohibits Technicians from engaging in personal activities while driving the Brink’s trucks. See id. at 92 (explaining that Technicians cannot use the Brink’s trucks for shopping). Further, in contrast to ordinary commuters and the state employees in Anderson, Technicians receive jobsite *49assignments at home via voice mail or handheld computer. Id. at 479-80, 484, 488, 494. They must spend time writing down the assignments and mapping the best route to reach their installation or service locations before beginning their drive. Id. In addition to the restrictions on Technicians’ drive time, Technicians remain “on duty” during the drive. Supervisors may redirect Technicians under the HDP while en route to and from their homes to assist with other jobs or answer service calls. E.g., id. at 273, 281-82.
¶16 The undisputed facts establish that Technicians were “on duty” during the drive time for purposes of WAC 296-126-002(8). Technicians are performing company business during the drive time because Brink’s strictly controls the drive time, prevents Technicians from using the trucks for personal business, and requires Technicians to remain available to assist at other jobsites while en route to and from their homes. Thus, we must next determine whether the Brink’s trucks constitute the employer’s “prescribed work place” under the WAC definition of “hours worked.”
¶17 Driving the trucks is an integral part of the work performed by Technicians. The nature of Brink’s’ business requires Technicians to drive the Brink’s trucks to reach customers’ homes and carry the tools and equipment necessary for servicing and installing home alarm systems. Technicians in the HDP report to the Kent office only once each week to refill supplies and attend the weekly company meeting. CP at 61 n.l. In addition, the Brink’s trucks serve as the location where Technicians often complete work-related paperwork because company policy dictates that employees must complete all paperwork either at the customer’s home or in the Brink’s truck. See id. at 668. Finally, like a work premises, Brink’s requires employees in the HDP to “ensure that the vehicle is kept clean, organized, safe and serviced.” Id. at 74. Based on these undisputed facts, we hold that the Brink’s trucks constitute a “prescribed work place” under WAC 296-126-002(8).
¶18 We conclude that Technicians were “on duty” at a “prescribed work place” during the drive time and therefore *50entitled to compensation under the MWA for the hours worked. Accordingly, we affirm the trial court’s grant of Technicians’ motion for summary judgment on the drive time claims.
B. Award of Prejudgment Interest
¶19 Brink’s contends that the trial court erred by awarding Technicians prejudgment interest for “all back wages ... on unpaid hours worked.” CP at 828. Courts award prejudgment interest when claims are liquidated. Hansen v. Rothaus, 107 Wn.2d 468, 472, 730 P.2d 662 (1986). A liquidated claim exists when “the amount of prejudgment interest can be determined from the evidence with exactness and without reliance on opinion or discretion.” Bostain, 159 Wn.2d at 723 (citing Hansen, 107 Wn.2d at 472). “ ‘A dispute over the claim, in whole or in part, does not change the character of a liquidated claim to unliquidated.’ ” Id. (quoting Hansen, 107 Wn.2d at 472). In Bostain, we affirmed the trial court’s award of prejudgment interest when the plaintiffs submitted objective evidence of the overtime due and the basis for the calculations. See id.
¶20 Here, Brink’s contends that the amount owed on the drive time claim required a jury to rely on opinion or discretion and was therefore unliquidated. At trial, the jury relied on an expert’s testimony calculating drive times with the software program “Mappoint.” Brink’s contends this data was insufficient to constitute a liquidated claim entitled to prejudgment interest.
¶[21 The Court of Appeals recently rejected a similar argument regarding unpaid overtime hours for employees improperly exempted under the MWA. McConnell v. Mothers Work, Inc., 131 Wn. App. 525, 536, 128 P.3d 128 (2006) (“Damages are liquidated if the evidence furnishes data that, if believed, made it possible to compute the amount owed with exactness.”). In McConnell, the court determined that the overtime hours were liquidated because the overtime payments were “determinable by computation” based on the hours worked and the fixed hourly rate. Id. at 536. *51Similarly, the drive time payments in the instant case were determinable based on the drive times calculated with Mappoint and Technicians’ actual wage rates. Because the jury did not have to rely on “opinion or discretion” to calculate the amount, we affirm the trial court’s determination that the drive time claim was liquidated.
C. Prejudgment and Postjudgment Interest Rate
¶22 Brink’s also challenges the trial court’s prejudgment and postjudgment interest award at the rate of 12 percent as provided in RCW 19.52.020(1). Brink’s contends that the trial court should have assessed the lower interest rate (two percent over the six-month treasury bill rate) provided in RCW 4.56.110(3), which applies to “[jjudgments founded on the tortious conduct of individuals or other entities.” This statute does not define “tortious conduct.”
¶23 We have not addressed the question of whether violations of the MWA constitute “tortious conduct” for purposes of determining whether RCW 4.56.110(3) affects the interest rate on such judgments. We have, however, decided that MWA violations do not constitute “tortious conduct” in determining the appropriate statute of limitations. Seattle Prof’l Eng’g Employees Ass’n v. Boeing Co., 139 Wn.2d 824, 838, 991 P.2d 1126, 1 P.3d 578 (2000) (SPEEA). In SPEEA, we held that MWA claims are more akin to unjust enrichment claims than to tort claims; “in instituting this action, the employees are in essence seeking recovery under an obligation imposed by law, and the [W]MWA, for Boeing’s unjust enrichment (i.e., receiving the benefit of the employees’ work without paying for the work.).” Id. We concluded that the employees’ claims for the unpaid work were subject to the statute of limitations for implied contracts, not tortious conduct.
¶24 Technicians in the present case sought damages under the MWA, essentially claiming that Brink’s was unjustly enriched by not paying them for hours worked. In accordance with SPEEA, we regard the nature of Technicians’ claims as implied contracts, not tortious conduct. *52Because the judgment was not “founded on tortious conduct,” we affirm the trial court’s assessment of the 12 percent interest rate.
D. Attorney Fees and Costs
¶25 We affirm the trial court’s order granting partial summary judgment for the drive time claim and the trial court’s award of attorney fees and costs for that issue. In addition, we grant Technicians’ request for attorney fees and costs incurred from this appeal under RAP 18.1, RCW 49.46.090(1) (requiring employer to pay reasonable attorney fees and costs when employer fails to pay the employee the required wages), and RCW 49.48.030 (providing for attorney fees when employee successfully recovers judgment for wages and salary).
CONCLUSION
¶26 We affirm the trial court’s rulings., Under the WAC definition of “hours worked,” we conclude that Technicians were entitled to summary judgment on the drive time issue because the uncontested facts establish that Technicians in the HDP were “on duty” at a “prescribed work place” during the drive time. We also affirm the trial court’s award of prejudgment interest, the prejudgment and postjudgment interest rate, and the award of attorney fees and costs. Finally, we award Technicians attorney fees and costs for their appeal.
Alexander, C.J., and C. Johnson, Bridge, Chambers, and Fairhurst, JJ., concur.