Having issues calculating this one.

Buy-rite pharmacy has purchased a small auto for delivering prescriptions. The auto was purchased for $25,000 and will have a 6-years useful life and a $5, 400 salvage value. Delivering prescriptions (which the pharmacy has never done before) should increase gross revenues by at least $33, 400 per year. the cost of these prescriptions to the pharmacy will be about $27,000 per year. the pharmacy depreciates all assets using the straight-line method. The payback period for the auto is closest to: 4.5 years 3.5 years 5.4 years 5 years