Revision of Depreciation On January 1, 2017, Slade Inc. purchased a machine for $90,000. Slade depreciated the machine with the straight-line depreciation method over a useful life of 10 years, using a residual value of $4,000. At the beginning of 2019, a major overhaul, costing $35,000, was made. After the overhaul, the machine's residual value is estimated to be $2,500, and the machine is expected to have a remaining useful life of 12 years.