company buys machinery for USD 60,000 on December 31, Year 1. Depreciation using the straight line method is to be applied. It is estimated that the machine's useful life will be six years and its residual value will be USD 6,000. Two years later (December 31, Year 3), the useful life is revised downward to three remaining years. The machine is sold for USD 25,000 on December 31, Year 5. What is the profit on disposal?