On Jan. 1, 2014, Westerfeld Company placed into service a machine that had an acquisition cost of $60,000, a salvage value of $6,000, and an estimated useful life of 5 years. On Jan. 1, 2016, Westerfeld revised the estimated useful life of the machine to 6 years. How much annual depreciation expense should Westerfield recognize for 2016, using straight-line depreciation