The expected rates of return on portfolios A and B are 11% and 14%, respectively. Further, portfolio A has a beta of 0.8 and a standard deviation of 10% while portfolio B has a beta of 1.5 and standard deviation of 31%. The expected rate of return on the S&P500 index is 12% and the T-bill rate is 6%. The S&P500 index has a standard deviation of 20%. (a) If you currently hold a market index portfolio, would you choose to add either of the two portfolios to your holdings? Explain. (b) Suppose instead that you can only invest in T-bills and one of either portfolio A, portfolio B, or the S&P500 index. Which of the three would you choose? Explain.