Concentric circles!

For three concentric circles $'C1'$ , $'C2'$ and $'C3'$ with radius $'1'$ , $'r'$ and $'9'$ respectively. If from a point $'A'$ on $'C3'$ a pair of tangents to circle $'C2'$ are drawn to touch at $B$ and $C$ such that $BC$ is tangent to circle $'C1'$ , then find $10r$ [For $1$ < $r$ < $9$ ]