The straight-line depreciation expense for year 3 is $4,000. The correct answer is d. $4,000.
To calculate straight-line depreciation, you can use the formula:
Depreciation Expense= Cost−Residual Value/ Useful Life
​In this case:
Cost of the equipment = $22,000
Residual Value = $2,000
Useful Life = 5 years

Therefore, the straight-line depreciation expense for year 3 is $4,000. The correct answer is d. $4,000.