For fiscal year 2015, Walmart Stores Inc. (WMT) had total revenues of $500.0 billion, net income of $20.00 billion, total assets of $203.49 billion, and total shareholder's equity of $90.00 billion.a. Calculate Wal-Mart's ROE directly, and using the DuPont Identity.b. Comparing with the data for Costco in problem 18, use the DuPont Identity to understand the difference between the two firms' ROEs.