Assume that you manage a risky portfolio with an expected rate of return of 15% and a standard deviation of 31%. The T-bill rate is 5% A client prefers to invest in your portfolio a proportion (%) that maximizes the expected return on the overall portfolio subject to the constraint that the overall portfolio's standard deviation will not exceed 20%. a. What is the investment proportion, y? (Do not round intermediate calculations. Round your answer to 2 decimal places.) Investment proportion y % b. What is the expected rate of return on the overall portfolio? (Do not round intermediate calculations. Round your answer to 2 decimal places.) Rate of return %