cardinal industries purchased a generator that cost $23,000. it has an estimated life of 5 years and a residual value of $3,000. it is estimated that it will be good for 5,000 hours. compute the depreciation expense for the first year using the units-of-activity method of depreciation assuming the generator was used for 1,000 hours. a.$5,200 b.$12,000 c.$4,000 d.$400