Eddison Inc. purchased a capital asset for $220,000 in 20X2. Management estimated that the asset would have a 8-year life with an estimated residual value of $16,200. Management depreciated assets using the straight-line method and recorded a full year’s depreciation in the year of purchase. The tax rate is 20%.
Assume that in 20X4, management was reviewing its policies relating to its capital asset accounts. Consider the following independent scenarios:
Scenario A 

Management decided to change the depreciation method to the declining-balance method, using a rate of 20%. This is a change in policy because the change is motivated by a desire to conform to industry practice.
Scenario B 

Management determined that the equipment was still in excellent condition and anticipated that the useful life has increased. Eddison Inc. now expects that they will be able to use the equipment for an additional year (i.e., 9 years in total). The residual value is now estimated to be $14,000.
Scenario C 

Management realized that when setting up the depreciation expense for the asset, they forgot to deduct the residual value.

Required:
1. Determine whether each case is a change in estimate, a change in policy, or an accounting error. Comment on whether each case is accounted for retrospectively or prospectively.
2. Calculate the 20X4 depreciation expense.
3. Calculate the impact on opening retained earnings for 20X2–20X4 (if required).