Equipment with a cost of $87,170, an estimated residual value of $6,123, 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 O $48,628.20 O 54.282.42 O < 538341.80 O 4 $3,854.18