Analysts have provided you the following forecasts for the economy and Stock A: (1) the probability of having a recession next year is 30 percent, a normal economy is 55 percent, and an expansion is 15 percent, and (2) the returns of Stock A will be -25% if the economy is in recession, 25% if the economy is normal, and 50% if the economy is in expansion. What is the ex-ante standard deviation of Stock A's returns? Select one: a. 7.17% b. 13.75% c. 37.08% d. 26.78%