Wardell Company purchased a mainframe on January 1, 2016, at a cost of $48,000. The computer was depreciated using the straight-line method over an estimated five-year life with an estimated residual value of $3,000. On January 1, 2018, the estimate of useful life was changed to a total of 10 years, and the estimate of residual value was changed to $1,200. Required: 1. Prepare the year-end journal entry for depreciation in 2018. No depreciation was recorded during the year. 2. Prepare the year-end journal entry for depreciation in 2018. Assume that the company uses the sum-of-the-years' -digits method instead of the straight-line method.