Profit from small sale ignores fixed costs and unspecified variable costs Steps:

• Identify revenue: 4 units sold for $500 total.
• Note fixed costs ($1000) are sunk and not attributable to this specific small sale.
• Variable costs for 4 units unavailable (table starts at 100 units), so assume negligible or zero for this transaction.
• Calculate profit as revenue minus relevant costs: $500 -$0 = $500.

Why A is correct:

• Profit from the sale equals revenue when fixed costs are not allocated and variable costs for low output are not specified, per marginal profit definition.

Why the others are wrong:

• B: Equals fixed costs, irrelevant to this sale.
• C: Equals fixed plus variable costs at 300 units, mismatched output.
• D: Equals fixed plus variable costs at 400 units, mismatched output.

Final answer: A