A factory machine was purchased for $216000 on January 1, 2022. It was estimated that it would have a $40000 salvage value at the end of its 5-year useful life. It was also estimated that the machine would be run 55000 hours in the 5 years. If the actual number of machine hours ran in 2022 was 5500 hours and the company uses the units-of-activity method of depreciation, the amount of depreciation expense for 2022 would be a. $21600. b. $17600. c. $35200. d. $43200.