Hypothesis Tests · Challenge problem

A two-sided $z$ test of $H_0\!: \mu = 100$ at $\alpha = 0.05$ (reject when $|z| > 1.96$) uses a sample of $n = 36$ from a population with $\sigma = 12$. In fact $\mu = 104$. Find the power of the test, counting rejections in BOTH tails. Round to four decimal places.