Machinery acquired new on January 1 at a cost of $100,000 was estimated to have a useful life of five years and a residual salvage value of $20,000. Straight-line depreciation was used. On January 1, following two full years of use of the machinery, management decided that the estimate of useful life had been too short and that the machinery would have to be retired after four more years, that is, at the end of the sixth year of service. Additionally, the market for the equipment had changed and management estimated that the salvage value at the end of the sixth year would be $10,000. Under this revised estimate, the depreciation expense for the third year of use would be: Select one: O a. $15,000 O b. $16,667 O c. $17,000 O d. $14,500