Answer: ER(X) = Rf + β(Rm-Rf)
        ER(X) = 6 + 1.2(16-6)
        ER(X) = 6 + 1.2(10)
        ER(X) = 6 + 12
        ER(X) = 18%
Explanation: The expected return on a stock equals risk-free rate plus the product of Beta and risk premium. Risk premium is the difference between market return(Rm) and risk-free rate(Rf). The expected rate of return on security X is 18%.