1 A three-year-old machine has a cost of $50,500, an estimated residual value of $1,500, and an estimated useful life of 35,000 machine hours. The company uses units-of-production depreciation and ran the machine 5,200 hours in year 1; 6,050 hours in year 2; and 7,600 hours in year 3. Calculate the net book value at the end of the third year. ints Net book value eBook