16-16 ratio analysis 16-16. (Ratio analysis) Assuming a 360-day year, calculate what the average investment in inventory would be for a firm, given the following information in each case. a. The firm has sales of $600,000, a gross profit margin of 10 percent, and an inventory turnover ratio of 6. b. The firm has a cost-of-goods-sold figure of $480,000 and an average age of inventory of 40 days. c. The firm has a cost-of-goods-sold figure of $1.15 million and an inventory turnover rate of 5. d. The firm has a sales figure of $25 million, a gross profit margin of 14 percent, and an average age of inventory of 45 days