A building with a cost of $900,000 has an estimated residual value of $360,000, has an estimated useful life of 36 years, and is depreciated by the straight-line method. a. What is the amount of the annual depreciation? Do not round intermediate calculations. $fill in the blank 1 b. What is the book value at the end of the twentieth year of use? $fill in the blank 2 c. If at the start of the twenty-first year