The Stock X is expected to earn 0.32 in boom, 0.16 in normal economy and -0.18 in bust. Stock Y is expected to earn 0.17 in boom, 0.12 in normal economy and -0.08 in bust. The probability of a boom is 5 percent, the probability of a normal economy is 91 percent and the probability of bust is 4 percent. What is the standard deviation of the returns on a portfolio that is invested in Stock X and Stock Y if the 30 percent of the portfolio is invested in Stock X and 70 percent is invested in Stock Y?

a. 8.46 percent

b. 5.15 percent

c. 6.24 percent

d. 7.18 percent

e. 4.32 percent