A machine with a cost of $171,000 has an estimated residual value of $19,000 and an estimated life of 5 years or 19,000 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 5,100 hours? Oa. $5,100 Ob. $51,000 Oc. $21,800 Od. $40,800