Calculate the book value of a three-year-old machine that cost $400,000, has an estimated residual value of

Question:

Calculate the book value of a three-year-old machine that cost $400,000, has an estimated residual value of $40,000, and has an estimated useful life of 20,000 machine hours. The company uses units-of-production depreciation and ran the machine 3,000 hours in year 1, 8,000 hours in year 2, and 6,000 hours in year 3?