Final answer:
The depreciation expense for Year 4 is $6,240, and the book value of the equipment at the end of Year 4 is $25,336.
Step-by-step explanation:
To compute the depreciation expense for Year 4, we first need to calculate the annual depreciation using the straight-line method. The formula for straight-line depreciation is:
Depreciation Expense = (Cost - Salvage Value) / Useful Life
For the first three years, the depreciation expense is:
Depreciation Expense = ($43,200 - $6,120) / 20 = $1,608 per year
Since new information suggests that the equipment will have a total useful life of 9 years, the remaining useful life in Year 4 is 9 - 3 = 6 years. The revised salvage value is $5,760. Therefore, the depreciation expense for Year 4 is:
Depreciation Expense = ($43,200 - $5,760) / 6 = $6,240 per year
To compute the book value of the equipment at the end of Year 4, we subtract the total depreciation expense for the first 4 years from the initial cost:
Book Value = Cost - (Depreciation Expense × Number of Years)
Book Value = $43,200 - ($1,608 × 3 + $6,240) = $25,336