Let $Y_{1}<Y_{2}<Y_{3}<Y_{4}$ be the order statistics of a random sample of size $n=4$ from a distribution with pdf $f(x ; \theta)=1 / \theta, 0<x<\theta$, zero elsewhere, where $0<\theta$. The hypothesis $H_{0}: \theta=1$ is rejected and $H_{1}: \theta>1$ is accepted if the observed $Y_{4} \geq c$.
(a) Find the constant $c$ so that the significance level is $\alpha=0.05$.
(b) Determine the power function of the test.