Which of the following is correct about accounting treatment of depreciation of fixed assets? O a. A change in useful life should be handled retrospectively and a change in residual value should be handled prospectively O b. A change in useful life should be handled prospectively and a change in residual value should be handled retrospectively O c. A change in depreciation method should be handled retrospectively and a change in residual value should be handled prospectively hy O d. A change in depreciation method should be handled prospectively and a change in residual value should be handled prospectively