explain the calculation for me

thanks in advance

You construct a portfolio containing two stocks, X and Y. You invest 30% of your funds in Stock X and the remainder in Stock Y. Stock X has an expected return of 7.1% and has a standard deviation of 14%. Stock Y has an expected return of 13.7% and has a standard deviation of 21%. The correlation coefficient between the two stocks is 0.3. What is the standard deviation of the returns on the portfolio? a. 16.46% b. 16.16% C. 15.79% d. 16.93% The correct answer is: 16.46%