7. Stone Crushing Company purchased a new machine on October 1, 2019, at a cost of $33,500. The company estimated that the machine will have a salvage value of $500. The machine is expected to be used for 150,000 working hours during its 5-year life. The machine usage was 30,000 hours in 2019 and 20,000 hours in 2020. Required: Compute the depreciation expense under the following methods for the year indicated. a) Straight-line for 2019 (1 Mark) b) Units-of-activity for 2019 and 2020. (1.5 Mark)