Detailed Answer
(a) From 1/1/01 to 12/31/Y3, depreciation was recorded
using an eight-year life. Yearly depreciation was $66,000
($528,000 ÷ 8), and accumulated depreciation at 12/31/Y1 was
$198,000 (3 × $66,000). In year 4, the estimated useful life was
changed to six years total with a salvage value of $48,000. Therefore,
the 12/31/Y3 book value ($528,000 – $198,000 =
$330,000) is depreciated down to the $48,000 salvage value over
a remaining useful life of three years (six years total – three years
already recorded). Depreciation expense for year 4 is $94,000
[($330,000 – $48,000) ÷ 3], increasing accumulated depreciation
to $292,000 ($198,000 + $94,000).