Given the following information, what is the standard deviation of a portfolio that is invested 20 percent in stock A, 65 percent in stock B, and 15 percent in stock C? If the state of economy is Boom, with the probability of 0.10, the rate of return for stock A is 17%, the rate of return for stock B is 12%, and the rate of return for stock C is 6%. If the state of economy is Normal, with the probability of 0.90, the rate of return for stock A is 12%, the rate of return for stock B is 9%, and the rate of return for stock C is 15%.