Why are those the correct answers

You are choosing among three retirement funds. Alpha Fund has an expected return of 21% and a standard deviation of 20%. Beta Fund has an expected return of 38% and a standard deviation of 60%. Gamma Fund has an expected return of 19%. If according to the mean-standard deviation rule the Gamma Fund would never be chosen, then the Gamma Fund's standard deviation must be greater than what? Gamma Fund's standard deviation must be greater than (Round to one decimal place.) Your retirement portfolio comprises 200 shares of the S\&P 500 fund (SPY) and 100 shares of iShares Barclays Aggregate Bond Fund (AGG). The price of SPY is $140 and that of AGG is $103. If you expect the return on SPY to be 8% in the next year and the return on AGG to be 6%, what is the expected return for your retirement portfolio? A. 7.84% B. 7.46% C. 161% D. 6.72%