a machine that cost $169,000 has an estimated residual value of $13,000 and an estimated useful life of 13,000 machine hours. the company uses units-of-production depreciation and ran the machine 3,000 hours in year 1, 4,000 hours in year 2, and 3,000 hours in year 3. required: calculate its book value at the end of year 3. (do not round intermediate calculations.)