\textbf{66.} In the figure below, if we close the switch K, the electric potential difference across the two terminals of the battery becomes how many times?
\textit{[Figure: Circuit with resistors $R$, $R$, $R$, switch $K$, internal resistance $r$, battery]}
\begin{itemize}
\item[(1)] $\dfrac{4}{5}$
\item[(2)] $\dfrac{5}{6}$
\item[(3)] $\dfrac{14}{15}$
\item[(4)] $\dfrac{15}{16}$
\end{itemize}