Selected comparative statement data for Willingham Products Company are presented below. All balance sheet data are as of December 31. 2011 2010 Net sales $760,000 $720,000 Cost of goods sold 480,000 440,000 Interest expense 7,000 5,000 Net income 50,000 42,000 Accounts receivable 120,000 100,000 Inventory 85,000 75,000 Total assets 580,000 500,000 Total common stockholders' equity 430,000 325,000 Need help with the following (a) Profit margin % (b) Asset turnover times (c) Return on assets % (d) Return on common stockholders' equity %