For each of the following pairs of investments, indicate which would always be preferred by a rational investor (assuming that these are the only investments available to the investor): a. Portfolio A Portfolio B r = 16% r = 12% 0 = 18% o = 18% Portfolio A Preference Portfolio B O Indeterminate b. Portfolio C Portfolio D r = 21% 19% o = 24% 0 = 18% Portfolio C Preference: Portfolio D Indeterminate c. Portfolio E Portfolio F r = 12% r = 0 = 18% 0 = 12% 12% Preference: Portfolio E Portfolio F O Indeterminate