Answer:
Reward to risk ratio = (Expected return - Risk free rate) / Beta
Reward to risk ratio of Y = ( 0.145 - 0.056) / 1.2
Reward to risk ratio of Y = 0.089 / 1.2
Reward to risk ratio of Y = 0.0741666
Reward to risk ratio of Y = 7.42%
Reward to risk ratio of Z = (0.093 - 0.056) / 0.7
Reward to risk ratio of Z = 0.037 / 0.7
Reward to risk ratio of Z = 0.0528571
Reward to risk ratio of Z = 5.29%
Security market line (SML) reward-to-risk ratio is the market risk premium itself which is 6.6%.
Stock Y has a reward-to-risk ratio that is higher than the market risk premium, it is currently under-valued in the market. Similarly, since stock Z has a reward-to-risk ratio that is lower than the market risk premium, it is currently over-valued in the market.