A portfolio consists of two securities: a risk-free asset and an equity security. The expected return on the risk-free asset is 4.75 percent. The expected return of the equity security is 17 percent with a standard deviation of 23 percent. What is the portfolio expected return if the standard deviation for the portfolio is 18 percent? a) 20.40% b) 18.00% c) 7.41% d) 14.34%