A three-year-old machine has a cost of $32,500, an estimated residual value of $1,900, and an estimated useful life of 34,000 machine hours. The company uses units-of-production depreciation and ran the machine 4,700 hours in year 1; 7,650 hours in year 2; and 6,700 hours in year 3. Calculate the net book value at the end of the third year.