$4,000
Depreciation Expense = (Cost - Salvage Value)/Estimated Useful Life
Depreciation Expense = ($24,000 - $4,000)/5 = $4,000

Depreciation Expense is the amount of the cost of an asset that is allocated over its useful life. The calculation for depreciation expense is Cost less Salvage Value (the estimated amount the asset can be sold for at the end of its useful life) divided by the estimated useful life of the asset. In this case, the cost of the asset is $24,000, the salvage value is $4,000 and the estimated useful life is 5 years. Therefore, the yearly depreciation expense is ($24,000 - $4,000)/5 = $4,000.