A machine that cost $324,000 has an estimated residual value of $18,000 and an estimated useful life of 18,000 machine hours. The company uses units-of-production depreciation and ran the machine 3,000 hours in year 1,5,000 hours in year 2. and 7,000 hours in year 3 . Required: Calculate its book value at the end of year 3. (Do not round intermediate calculations.)