Cullumber Medical manufactures hospital beds and other institutional furniture. The company's comparative balance sheet and income statement for 2019 and 2020 follow. Cullumber Medical Comparative Balance Sheet As of December 31 2020 2019 Assets Current assets Cash Accounts receivable, net Inventory Other current assets Total current assets Property, plant, & equipment, net Total assets $390,000 1,038,000 746,000 381,350 2,555,350 8,702,250 $11,257,600 $417,500 776,450 681,100 247,050 2,122,100 8,439,880 $10,561,980 $2,846,100 3.892,600 Liabilities and Stockholders' Equity Current liabilities Long-term debt Total liabilities Preferred stock, $5 par value Common stock, $0.25 par value Retained earnings Total stockholders' equity Total liabilities and stockholders' equity $3,196,000 3,702,700 6,898,700 58,950 104,700 4,195,250 4,358,900 $11,257,600 6,738,700 58,950 103,800 3,660,530 3,823,280 $10,561,980 Cullumber Medical Comparative Income Statement and Statement of Retained Earnings For the Year 2020 2019 Sales revenue (all on account) $10,177,200 $9,613,950 Cost of goods sold 5,611,600 5,298,700 Gross profit 4,565,600 4,315,250 Operating expenses 2,840,200 2,634,200 Net operating income 1,725,400 1,681,050 Interest expense 300,300 308,650 Net income before taxes 1,425,100 1,372,400 Income taxes (30%) 427,530 411,720 Net income $997,570 $960,680 Dividends paid Preferred dividends 29,550 29,550 Common dividends 433,400 413,000 Total dividends paid 462,950 442,550 Net income retained 534,720 518,130 Retained earnings, beginning of year 3,660,530 3,142,400 Retained earnings, end of year $4,195,250 $3,660,530 Calculate the following profitability ratios for 2020. (Round answers to 1 decimal place, e.g. 50.1%.) % a. Gross margin percentage % b. Return on assets % C. Return on common stockholders' equity