You have a three-stock portfolio. Stock A has an expected return of 11 percent and a standard deviation of 36 percent, Stock B has an expected return of 15 percent and a standard deviation of 41 percent, and Stock C has an expected return of 15 percent and a standard deviation of 41 percent. The correlation between Stocks A and B is 0.30, between Stocks A and C is 0.20, and between Stocks B and C is 0.05. Your portfolio consists of 42 percent Stock A, 25 percent Stock B, and 33 percent Stock C. Calculate the expected return and standard deviation of your portfolio. The formula for calculating the variance of a three-stock portfolio is:

_p² = x_A² _A² + x_B² _B² + x_C² _C²+ 2x_Ax_BABCorr(R_A,R_B) +2x_Ax_CACCorr(R_A,R_C) + 2x_Bx_CBCCorr(R_B,R_C)

The problem asks for the expected return and standard deviation. I know the expected return is 13.32, but I got 22.73 for the standard deviation and that's incorrect.

So what is the standard deviation?