3.58: Perpendicular bisector of $PQ$; points $R,S$

Points $P$ and $Q$ have coordinates $(-5, 12)$ and $(15, -6)$. Point $R$ lies on the perpendicular bisector of $PQ$ and has $x$-coordinate $7$. Find the $y$-coordinate of $R$.

Point $S$ on the perpendicular bisector is such that its distance from $PQ$ is $3$ times the distance of $R$ from $PQ$. Find the two possible coordinates of $S$.