\textbf{30.} In the figure below, two tangent lines are drawn from point $A$. What is the radius of the circle?
\textit{[Figure: Two tangent lines drawn from external point $A$ to a circle, with segments labeled 9, 8, 7 and point $B$, $C$ marked]}
\begin{itemize}
\item[(1)] $7/2\sqrt{2}$
\item[(2)] $4/8\sqrt{5}$
\item[(3)] $3/6\sqrt{2}$
\item[(4)] $2/4\sqrt{5}$
\end{itemize}