$2,875
Formula (Cost – Residual Value) / Estimated Life = Annual Depreciation
Depreciation for the first three years = [($20,000 - $5,000) ÷ 10] × 3 = $4,500
Book value at the end of the fourth year = $20,000 - $4,500 = $15,500
Depreciation expense the third year = ($15,500 - $4,000) / 4 = $2,875 per yr.