Exercise 9-19 (Part Level Submission) life, Whippet Bus Lines uses the units-of-activity method in depreciating its buses. One bus was purchased on January 1, 2017, at a cost of $128,000. Over its 4-year useful life the bus is expected to be driven 213,750 miles. Salvage value is expected to be $8,300 (a) Compute the depreciation cost per unit. (Round answer to 3 decimal places, e.g. 6.251) Depreciation cost per unit s