Calculate the book value of a four-year-old machine that cost $21,000, has an estimated residual value of

Question:

Calculate the book value of a four-year-old machine that cost $21,000, has an estimated residual value of $1,000, and has an estimated useful life of 20,000 machine hours. The company uses units-of-production depreciation and ran the machine 3,200 hours in year 1, 7,050 hours in year 2, and 7,500 hours in year 3.