Restate the following income statement for a retailer in contribution format. Sales revenue ($50 per unit) $ 65,000 Less cost of goods sold ($16 per unit) 20,800 Gross margin 44,200 Less operating costs: Commissions expense ($3 per unit) $ 3,900 Salaries expense 8,000 Advertising expense 2,500 Shipping expense ($2 per unit) 2,600 18,000 Operating income $ 27,200