Answer:
1. Compute the annual depreciation expense prior to the change in estimates.
annual depreciation = ($396,000 - $36,000) / 50 = $7,200 per year
2. Compute the annual depreciation expense after the change in estimates.
annual depreciation = ($324,000 - $30,000) / 20 = $14,700 per year
3. What will be the net effect of changing estimates on the balance sheet, net income, and cash flows for the year?
Any changes in an asset's useful life are reported prospectively, this means that they do not affect any past records, only future records are affected. In this case, the depreciation expense per year will increase form $7,200 to $14,700, so net income will be negatively affected by it. Cash flows will not be affected, since depreciation expense is a non-cash expense. P,P&E on the balance sheet will be affected because the net value of the building will decrease faster.