Equipment with a cost of $76,667, an estimated residual value of $5,592, and an estimated life of 12 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. $35,537.50 Ob. $3.427.46 O c. $4,569.94 9 d. 514709.85