Equipment with a cost of $78,829, an estimated residual value of $4,720, and an estimated life of 13 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

a.$11,156.21

b.$3,432.68

c.$4,958.32

d.$34,204.15