Suppose we have three portfolios, plus a risk-free asset that pays an expected return of 3% per year with a standard deviation of zero. a offers an expected return of 15% per year, with a standard deviation of 30% per year. b offers an expected return of 10% per year, with a standard deviation of 20% per year. c offers an expected return of 5% per year, with a standard deviation of 10% per year. suppose that a client asks you to choose a portfolio with an expected return of 39% per year, and as low a standard deviation as possible. which of a, b, and c do you include in the client's portfolio? why? what standard deviation can you achieve?