I got this right but please help explain

Question 5 2/2 pts Use the following information for problems 3 through 10: The risk-free rate of return is 4%, the required rate of return of the market portfolio is 10%. You invest $10,000 in stock A, $15,000 in stock B, $50,000 in stock C, and $50,000 in stock D. The average returns and standard deviations of the individual stocks are as follows: Ret Standard Deviation Beta Stock A 0.25 0.31 2.0 Stock B 0.16 0.36 1.0 Stock C 0.04 0.17 0.8 Stock D 0.02 0.08 0.3 What is the beta of this portfolio? O 0.72 0.54 0.62 01.10