Equipment with a cost of $83,647, an estimated residual value of $5,994, and an estimated life of
10 years was depreciated by the straight-line method for 6 years. Due to obsolescence, it was
determined that the remaining useful life should be shortened by 3 years and the residual value
changed to zero. The depreciation expense for the current and future years is
Oa. $3,705.52
Ob. $4,117.24
Oc. $37,055.20
Od. $46,591.80