Restate the following income statement for a retailer in contribution format. Sales revenue ($100 per unit) Less cost of goods sold ($60 per unit) Gross margin Less operating costs: Commissions expense ($7 per unit) $ 7,000 $ 100,000 60,000 40,000 Salaries expense 7,800 Advertising expense 5,800 Shipping expense ($3 per unit) 3,000 23,600 Operating income $ 16,400