In recent years, Martinez Transportation purchased three used buses. Because of frequent turnover in the accounting department, a different accountant selected the depreciation method for each bus, and various methods were selected. Information concerning the buses is summarized as follows. For the declining-balance method, the company uses the double-declining rate. For the units-of-activity method, total miles are expected to be 117,000. Actual miles of use in the first 3 years were 2019,27,500;2020,35,000; and 2021,31,500. (a1) Your answer is correct. For Bus \#3, calculate depreciation expense per mile under units-of-activity method. (Round answer to 2 decimal places, e.g. 0.50.) Depreciation expense $ per mile Compute the amount of accumulated depreciation on each bus at December 31,2020 . (Round answers to 0 decimal places, e.g. 2,125.)