Since 2016, DS Tech's return on common stockholders' equity has been 20%. During that time, DS had no preferred stock and 20,000 shares of $5 par common stock issued and outstanding. In 2020, DS' return increased to 25% as a result of action taken by the company in that year. Which of the following could have produced the increase? Assume static net income. the issuance of preferred stock an increase in retained earnings a purchase of treasury stock the addition of common stock dividends distributable