Revision of Depreciation Equipment with a cost of $673,200 has an estimated residual value of $61,200, has an estimated useful life of 40 years, and is depreciated by the straight-line method. a. Determine the amount of the annual depreciation. b. Determine the book value after 22 full years of use. c. Assuming that at the start of the year 23 the remaining life is estimated to be 26 years and the residual value is estimated to be $58,400, determine the depreciation expense for each of the remaining 26 years.