Question 4 (Mandatory) (7 points) According to Investment Digest ("Diversification and the Risk/Reward Relationship", Winter 1994, 1-3), the mean of the annual return for common stocks from 1926 to 1992 was 16.5%, and the standard deviation of the annual return was 19%. a. What is the probability that the stock returns are greater than 0%? b. What is the probability that the stock returns are less than 18%? ( P(X > 0) = 19.2%; P(X 0) = 80.7%; P(X 0) = 29.7% ; P(X 0) = 86.7%; P(X