Answer: The developer’s percentage of profit was 71.43%.
step by step: The total cost of the lots was $28,000 * 5 = $140,000. The developer then subdivided the lots into 10 lots, each with 120/2 = 60 front feet. The developer sold each lot for $400 per front foot, so each lot sold for $400 * 60 = $24,000. The total revenue from selling all 10 lots was $24,000 * 10 = $240,000. The developer’s profit was $240,000 - $140,000 = $100,000.