Detailed Answer
(a) The requirement is to calculate the amount of
depreciation expense to be recorded in year 5. After three years
(year 2-year 4), accumulated depreciation is $72,000. Therefore,
the method that was used was the sum-of-the-years’ digits (SYD)
method. Using this method, after three years the balance in accumulated
depreciation would be 12/15 of the depreciable base
(5/15 + 4/15 + 3/15). The depreciable base is the cost
($110,000) less the residual value ($20,000), or $90,000. Thus,
using the SYD method, accumulated depreciation at 12/31/Y4
would be $72,000 ($90,000 × 12/15), which matches the
amount given in the problem. Year 5 depreciation expense, using
the SYD method is $12,000 ($90,000 × 2/15).