d. Consider two portfolios, x and y, whose convex combinations compose the envelope frontier in the graph below (curve ABC). Also marked, are other portfolios, some of which contain short positions of either x or y. Do you agree with the statement Every convex combination of any two efficient portfolios is efficient"? Explain your answer. 16% 14% 12% 10% 8% B 6% C 4% 20% 25% 30% 35% 40% 45% 50% 55% 60%