Equipment with a cost of $609,300 has an estimated residual value of $65,300, has an estimated useful life of 20 years, and is depreciated by the straight-line method. a. Determine the amount of the annual depreciation. b. Determine the book value after 7 full years of use. c. Assuming that at the start of the year 8 the remaining life is estimated to be 17 years and the residual value is estimated to be $56,800, determine the depreciation expense for each of the remaining 17 years.