The cost of equipment purchased by Charleston, Inc., on June 1, 2012 is $89,000. It is estimated that the machine will have a $5,000 salvage value at the end of its service life. Its service life is estimated at 7 years; its total working hours are estimated at 42,000 and its total production is estimated at 525,000 units. During 2012 the machine was operated 6,000 hours and produced 55,000 units. During 2013 the machine was operated 5,500 hours and produced 48,000 units