Harris Corporation had net income of $230,000 and paid dividends of $50,000 to common stockholders and $20,000 to preferred stockholders in 2010. Harris Corporation's common stockholders' equity at the beginning and end of 2010 was $870,000 and $1,130,000, respectively. There are 100,000 weighted-average shares of common stock outstanding. what was the Harris Corporation's return on common stockholders' equity ?