portfolio's A and Bare 12% and 16% respectively. The beta of A is 0.7 , while that of B is 1.4. The T-bill rate currently is 500, whereas the expected rate of return of S&P 500 index is 13%. The standard deviation of the portfolio A is 12% that of B is 31% and that of S&P 500 index s 18%. (a) If you currently hold market-index portfolio, would you choose to add either of these portfolio's to your holdings? (b) If instead you could invest only in T-bills and one of these portfolios, which would you choose