The following table presents sales revenue, cost of goods sold, and inventory amounts for three retailers of fine jewelry, Tiffany & Co. Zale Corporation, and Blue Nile, Inc. (an Internet retailer). (S millions) Tiffany & Co. 2013 2012 Revenues Cost of goods sold Inventory $4,364 $4,016 777 1,673 2471 2.333 Zale Corporation Revenues Cost of goods sold 9 Inventory $1.974 $1,909 948 822 770 Blue Nile, Inc Revenues Cost of goods sold 45 Inventory $504 $442 367 61 89 a. Compute the gross profit margin (GPM) for each of these companies for 2013 and 2012 Tiffany Zale Blue Nile 2013 2012 2013 2012 2013 2012 Gross proft 2587 2343 984 961 52 75 Gross profit margin (GPM) 59.3 % 58.3 % 49.8 % 50.3 % 10.3 % 17 %