1. Let $\{Y1, \ldots, Yn\}$ be a random sample from the normal distribution with mean $\mu$ and known variance $\sigma^2$. The hypotheses are $H0: \mu = 50$ vs $Ha: \mu > 50$ and the rejection region $R = \{\hat{y}: \hat{y} > 50 + a\}$. At 0.05 level of significance, the value of $a$ is (5%) and the power of the test for true $\mu = 60$ is . (5%) (若無法算出一個值，請用累積密度函數等方式表達)