7-16. A special-purpose milling machine is to be depreciated as a linear function of use (units-of-production method). It costs $90,000 and is expected to produce 250,000 units and then be sold for $8,000. Up to the end of the third year, it had produced 80,000 units, and during the fourth year it produced 20,000 units. What is the depreciation deduction for the fourth year and the BV at the end of the fourth year? (7.3)