what formula or concept can I used to check which portfolio is on the efficient frontier?

29.- Consider the following probability distribution for stocks A and B:+ * + State Probability Return on Stock A Return on Stock B 1 0.10 10% 8% 2 0.20 13% 7 3 0.20 12 6% 4 0.30 14% 99 5 0.20 150 8% + + Which of the following portfolio(s) is(are) on the efficient frontier? + + + A. The portfolio with 20 percent in A and 80 percent in B. B. *The portfolio with 15 percent in A and 85 percent in B. C. *The portfolio with 26 percent in A and 74 percent in B. D. The portfolio with 10 percent in A and 90 percent in B. E. A and B are both on the efficient frontier