13) Suppose that your friend has decided to construct a portfolio that will contain stock X, stock and the risk-free asset. The standard deviations of stock X and stock Y are 12% and 16% respectively, and the correlation between stock X and stock Y is 0.6. Your friend has decided to put 40% of his money on stock X, 30% on stock and the rest on the risk-free asset. What is the standard deviation of his portfolio? A. 8.59% B. 9.03% C. 10.88% D. 14.59%