5. A change in the eestimated useful life and residual value of machinery in the current year is as handled as

a retrospective change back to the date of acquisition as though the current estimated life and residual value had been used all along

b a prospective change from the current year through the remanibder of its useful life, using he ew estimates

c a cumulative adjustment to income int eh current year for the difference in depreciation under the new versus old estimates

d. none