A machine with a cost of $70,939 has an estimated residual value of $4,265 and an estimated life of 3 years or 14,416 hours. It is to be depreciated by the units-of-activity method. What is the amount of depreciation for the second full year, during which the machine was used 4,404 hours? Do not round your intermediate calculations. a. $22,224.67 b. $20,368.50 c. $21,671.43 d. $44,449.33