Equipment with a cost of $73,860, an estimated residual value of $5,315, and an estimated life of 12 years was depreciated by the straight-line method for 5 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. $5,662.45 Ob. 511,324.90 Oc. $28,560.42 Od. $3,774.97