Under SLN, Year 4 Tax Basis is still relatively high ($2,000), so selling for $2,300 minus a $500 fee yields a -$200 Pretax Loss ($2,300 - $2,000 - $500 = -$200), creating a +$50 tax shield (25% x $200) that reduces the firm's taxes ($2,300 - $500 + $50 = $1,850). Under DDB (Tax Basis $1,296) and MACRS (Tax Basis $1,728), faster early depreciation lowered the tax basis below the $1,800 net proceeds, resulting in taxable gains (+$504 and +$72) and tax expenses (-$126 and -$18).