A machine is purchased for `$36\ 000`. Its value depreciates at a rate of `$0.16` for each unit it produces. On average, the machine produces `24\ 000` units a year.
Using the unit cost method of depreciation, the value of the machine after six years of use is closest to
A. $3840
B. $7200
C. $12 960
D. $23 040
E. $32 160