Revision of Depreciation A building with a cost of $1,200,000 has an estimated residual value of $250,000, has an estimated useful life of 40 years, and is depreciated by the straight-line method. a. What is the amount of the annual depreciation? b. What is the book value at the end of the twenty-eighth year of use? c. If at the start of the twenty-ninth year it is estimated that the remaining life is 10 years and that the residual value is $180,000, what is the depreciation expense for each of the remaining 10 years?