Final answer:
The correct cumulative effect on prior years adjusted for the change in depreciation method is closest to $40,000 (not accounting for taxes in the options), and the depreciation expense for the year 2015 is $75,000.
Step-by-step explanation:
To solve these questions, we need to first calculate the depreciation expenses based on the original estimate, and then adjust them based on the new estimate that extended the useful life from six to eight years.
Originally, the depreciation per year would have been $600,000 divided by 6 (years) = $100,000 per year. For the first 3 years (2012, 2013, 2014), the accumulated depreciation would be $100,000 times 3 = $300,000. With the new estimate of 8 years, the annual depreciation would be $600,000 divided by 8 (years) = $75,000 per year. The accumulated depreciation for the first 3 years with the revised estimate would be $75,000 times 3 = $225,000. The difference between the original and revised accumulated depreciation amounts to $300,000 - $225,000 = $75,000. However, we need to consider the tax effect of this change. The tax effect would be $75,000 times the tax rate of 30%, which equals $22,500. Thus, the cumulative effect on prior years after accounting for taxes is $75,000 - $22,500 = $52,500
Based on the revised estimate, the annual depreciation is $75,000. As the change was made at the beginning of 2015, Swift would report $75,000 in depreciation expense for that year.
Given the provided choices, the closest answer to the cumulative effect (not adjusted for tax) is answer choice b. $40,000, and the depreciation expense for 2015 is answer choice b. $75,000.