Farm equipment with a cost of $225,000 has an estimated residual value of $15,000, an estimated useful life of six years, and is depreciated by the straight-line method. a. What is the amount of annual depreciation? b. What is the carrying amount at the end of the fourth year of use? c. At the start of the fifth year, $25,000 is spent on an engine upgrade so that the remaining useful life is four years and the estimated residual value is $5,000. What is the depreciation expense for the fifth year? d. At the start of the sixth year, the appraised value of the farm equipment is $60,000. What is the impairment loss?