A three-year-old machine has a cost of $36,000, an estimated residual value of $2,700, and an estimated useful life of 37,000 machine hours. The company uses units-of-production depreciation and ran the machine 3,700 hours in year 1; 6,950 hours in year 2; and 6,700 hours in year 3. Calculate the net book value at the end of the third year. Net book value