You are creating a portfolio of two stocks. The first one has a standard deviation of 10.0% and the second one has a standard deviation of 30.0%. The correlation coefficient between the returns of the two is -0.30. You will invest 70% of the portfolio in the first stock and the rest in the second stock. What will be the standard deviation of this portfolio's returns? Answer in percent, rounded to one decimal place (e.g., 4.32%=4.3).