Final answer:
The beta of the added security is calculated as the weighted average of the betas of the individual securities in the portfolio.
Step-by-step explanation:
To achieve the same beta as the market, we need to calculate the beta of the added security. The formula for the beta of a portfolio is the weighted average of the betas of the individual securities in the portfolio.
Given the investments in stock A, stock B, and the risk-free asset, the beta of the added security can be calculated as follows:
Beta of added security = (Total investment in stock A x Beta of stock A + Total investment in stock B x Beta of stock B) / Total investment in portfolio
Using the given values, the beta of the added security is calculated as follows:
Beta of added security = (280 x 1.03 + 1120 x 1.33) / (280 + 1120 + 840) = 1.24
Therefore, the beta of the added security is approximately 1.24, which is not one of the given options.