$(15$ points$)$ 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?