Wardell Company purchased a mainframe on January 1, 2016, at a cost of $40,000. The computer was depreciated using the straight-line method over an estimated five-year life with an estimated residual value of $4,000. 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 $500. Required: i. Calculated the book value as of 1/1/2018 (3) 2. Prepare the year-end journal entry for depreciation in 2018 using the revised estimates (3)