Circle

Let $c_1: x^2+y^2=1$ and $c_2:(x-10)^2+y^2=9$ be two circles a line touching $c_1$ at $P$ and $c_2$ at $Q$. If $M$ is the mid-point of $P Q$, then $M$ lies on a circle $(x-5)^2+y^2=r^2$ where ' $r$ ' is $(r>0)$