units of production double-diminishing-balance Ch06. Barlow Trail Corporation purchased office equipment on September 30, 2018, for a total cost of $50,500 Management estimated useful life at 15 years and residual value at $5,500. Straight-line depreciation is used and computed to the nearest whole month. Barlow Trail Corporation's year end is December 31. Required: a. Prepare the adjusting entry for depreciation on December 31, 2018. b. Early in 2020, management revised its estimates of useful life and residual value for the office equipment. Useful life was reduced to a total of 10 years, and residual value was reduced to $2,000. Prepare the adjusting entry for depreciation on December 31, 2020, using the revised estimate.