\textbf{173.} In the circuit below, ammeters $A_1$, $A_2$, $A_3$, and $A_4$ show currents $A$, $2A$, $12A$, and $9A$ respectively. How many amperes of current pass through resistor $R_V$?
\textit{[Figure: Circuit diagram with resistors $R_1$, $R_2$, $R_3$, $R_4$, $R_5$, $R_6$, $R_V$ and ammeters $A_1$, $A_2$, $A_3$, $A_4$]}
\begin{itemize}
\item[(1)] 3
\item[(2)] 4
\item[(3)] 8
\item[(4)] 11
\end{itemize}