Suppose that many stocks are traded in the market and that it is possible to borrow at the risk-free rate, rf. The characteristics of two of the stocks are as follows: Stock B Correlation = -1 Expected Return 6% 12% Standard Deviation 25% 75% a. Calculate the expected rate of return on this risk-free portfolio? (Hint: Can a particular stock portfolio be substituted for the risk-free asset?) (Round your answer to 2 decimal places.) Rate of return % b. Could the equilibrium rf be greater than 7.50%? O Yes O No