Equipment with a cost of $82,145, an estimated residual value of $6,588, and an estimated life of 10 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 4 years and the residual value changed to zero. The depreciation expense for the current and future years is Oa. 552,889.90 Ob. $2,925.51 Oc. $2,659 55 Od S-29.255.10