Comparative Income Statement for the Second Quarter April May June Sales in units 4,500 5,250 6,000 Sales revenue $630,000 $735,000 $840,000 252,000 294,000 336,000 Less: cost of goods sold 378,000 441,000 504,000 Gross margin Less: operating expenses Shipping expense Advertising expense 56,000 63,500 71,000 70,000 70,000 70,000 Salaries and commissions 147,500 166,250 185,000 Insurance expense 9,000 9,000 9,000 42,000 Depreciation expense Total operating expenses 42,000 42,000 324,500 355,250 377.000 Net income $53,500 $94,750 $127,000 Required: a. State the cost formula for Shipping and Salaries & Commissions. b. Prepare the contribution margin format statement for July, when the sales were 6,500 units