An investor purchased 550 shares of stock A at $22.50 per share and 1,050 shares of stock B at $30.50 per share one year ago. Stock A and stock B paid quarterly dividends of $2.50 per share and $2.00 per share, respectively, during the year. One year later, the investor sold both stocks at $30.50 per share. The correlation coefficient (_AB) is 0.3 and the standard deviations of stock A and stock B are 20.5 percent and 15.5 percent, respectively. Calculate the standard deviation of the portfolio. (Round intermediate calculations to 4 decimal places, e.g. 15.2512 and the final answer to 2 decimal places, e.g. 15.25%.)