Calculating Average Operating Assets, Margin, Turnover, and Return on Investment East Mullett Manufacturing earned operating income last year as shown in the following income statement: Sales $531,250 Cost of goods sold 280,000 Gross margin $251,250 Selling and administrative expense 191,500 Operating income $59,750 Less: Income taxes (40%) 23,900 Net income $35,850 At the beginning of the year, the value of operating assets was $390,000. At the end of the year, the value of operating assets was $460,000.