A three-year-old machine that has a cost of $38,300, an estimated residual value of $2,300, and an estimated useful life of 40,000 machine hours. The company uses units-of production depreciation and ran the machine 3,700 hours in year 1; 7,650 hours in year 2; and 8,500 hours in year 3.

Calculate the net book value at the end of the third year.