The 2010 balance sheet of E.I. du Pont de Nemours and Company shows average DuPont shareholders' equity of $8,247 million, net operating profit after tax of $3,435 million, net income attributable to DuPont of $3,031 million, and common shares issued of 1,004 million. Assume the company has no preferred shares issued. DuPont's return on equity (ROE) for the year is