Tilda Bus Lines uses the units-of-activity method in depreciating its buses. One bus was purchased on January 1, 2012, at a cost of $168,000. Over its 4-year useful life, the bus is expected to be driven 100,000 miles. Salvage value is expected to be $8,000.

Instructions
  (a) Compute the depreciation cost per unit.
  (b) Prepare a depreciation schedule assuming actual mileage was: 2012, 26,000; 2013, 32,000; 2014, 25,000; and 2015, 17,000.