Revision of Depreciation Equipment with a cost of $613,600 has an estimated residual value of $70,600, has an estimated useful life of 30 years, and is depreciated by the straight- line method. a. Determine the amount of the annual depreciation b. Determine the book value after 15 full years of use: c. Assuming that at the start of the Boar 16 the remaining life is estimated to be 23 years and the residual value is estimated to be $73,000, determine the depreciation expense for each of the remaining 23 years