Equipment with a cost of $66,150, an estimated residual value of $3,150, and an estimated life of 15 years was depreciated by the straight-line method for 7 years. Due to obsolescence, it was determined that the remaining useful life should be shortened by 5 years and the residual value changed to zero. The depreciation expense for the current and future years is a. $29,400 Ob. $12,250 Cc. $3,063 Od. $2,450