A circle $C$ has center at the origin and radius $4$. Another circle $K$ has a diameter with one end at the origin and the other end at the point $(0,15)$. The circles $C$ and $K$ intersect in two points. Let $P$ be the point of intersection of $C$ and $K$ which lies in the first quadrant. Let $(r, \theta )$ be the polar coordinates of $P$, chosen so that $r$ is positive and $0 \leq \theta \leq 2$. Find $r$ and $\theta$.

$r =$

$\theta =$