\textbf{130.} The image of circle $C$ with center $(1, 2)$ and radius 1 unit, under the transformation $T(x,y) = (3x, 3y)$, is circle $C'$. The length of the common external tangent of these two circles is what?
\begin{itemize}
\item[(1)] $3$
\item[(2)] $2\sqrt{3}$
\item[(3)] $4$
\item[(4)] $3\sqrt{2}$
\end{itemize}