Yello Bus Lines uses the units-of-activity method in depreciating its buses. One bus was purchased on January 1,2022 , at a cost of $232,544. Over its 4-year useful life, the bus is expected to be driven 137,100 miles. Salvage value is expected to be $7,700. (a) Compute the depreciable cost per unit. (Round answer to 2 decimal places, e.8. 0.50.) Depreciable cost per unit $ per mile