Return on equity is a ratio that: O A. cannot be calculated if the company has preferred shares in addition to common shares O B. is calculated by dividing net income plus preferred dividends by average common shareholders' equity O C. shows the relationship between net income available for common shareholders and average common shareholders' equity O D. is cakculated by dividing net income plus preferred dividends by average common shareholders' equity and shows the relationship between net income available for common shareholders and average common shareholders' equity