In fiscal year 2018, Wal-Mart Stores (WMT) had revenue of $514.41 billion, gross profit of $129.10 billion, and net income of $6.67 billion. Costco Wholesale Corporation (COST) had revenue of $141.6 billion, gross profit of $18.42 billion, and net income of $3.13 billion. a. Compare the gross margins for Walmart and Costco. b. Compare the net profit margins for Walmart and Costco. c. Which firm was more profitable in 2018 ? a. Compare the gross margins for Walmart and Costco. The gross margin for Walmart is %. (Round to two decimal places.) The gross margin for Costco is %. (Round to two decimal places.) b. Compare the net profit margins for Walmart and Costco. The net profit margin for Walmart is %. (Round to two decimal places.) The net profit margin for Costco is %. (Round to two decimal places.) c. Which firm was more profitable in 2018 ? (Select from the drop-down menu.) was more profitable in 2018