Required: A machine that cost $360,000 has an estimated residual value of $40,000 and an estimated useful life of four years. The company uses straight-line depreciation. Calculate its book value at the end of year 3 . (Do not round intermediate calculations.) Required: A machine that cost $360,000 has an estimated residual value of $40,000 and an estimated useful life of four years. The company uses straight-line depreciation. Calculate its book value at the end of year 3 . (Do not round intermediate calculations.)