A three-year-old machine has a cost of $37,900, an estimated residual value of $1,600, and an estimated useful life of 33,000 machine hours. The company uses units-of-production depreciation and ran the machine 5,100 hours in year 1; 7,250 hours in year 2; and 6,600 hours in year 3. Calculate the net book value at the end of the third year