A three-year-old machine has a cost of $39,800, an estimated residual value of $1,300, and an estimated useful life of 35,000 machine hours. The company uses units-of-production depreciation and ran the machine 4,000 hours in year 1; 6,750 hours in year 2; and 7,900 hours in year 3. Calculate the net book value at the end of the third year.