The Jefferson Co. purchased a machine on January 1, 2020. The machine cost $595,000. It had an estimated life of ten years, or 30,000 units, and an estimated residual value of $40,000. In 2020 , Jeffries produced 3,000 units. Required: Compute the depreciation charge for 2020 using each of the following methods: a. Double-declining-balance method b. Activity method (units of output) c. Sum-of-the-years'-digits method d. Straight-line method