Final answer:
To determine the proportion of the optimal risky portfolio invested in stock B, we use the concept of the capital market line (CML) and the Sharpe ratio. Based on the given values, the proportion of the optimal risky portfolio invested in stock B is approximately 48%.
Step-by-step explanation:
In order to determine the proportion of the optimal risky portfolio that should be invested in stock B, we need to use the concept of the capital market line (CML). The CML represents the efficient frontier of risky assets combined with the risk-free asset. The optimal risky portfolio is the point on the CML with the highest Sharpe ratio, which is the ratio of excess return to standard deviation.
To calculate the proportion of the optimal risky portfolio invested in stock B, we need to use the formula: proportion of stock B = (expected return of stock B - risk-free rate) / (expected return of stock B - expected return of stock A). Using the given values, the proportion of the optimal risky portfolio that should be invested in stock B is approximately 48% (option b).