Equipment with a cost of $80,035, an estimated residual value of $5,415, and an estimated life of 15 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 4 years and the residual value changed to zero. The depreciation expense for the current and future years is a.$10,037.40 b.$29,848.00 c.$5,018.70 d.$3,345.80