\textbf{186-} At a power plant, the voltage is $10000$ V, which is converted by transformer A to $400000$ V and then transmitted to a city. In the city, transformer B converts the voltage to $5000$ V. If the ratio of the number of turns in the primary to secondary coil in transformer A is $K_A$, and in transformer B is $K_B$, then $\dfrac{K_A}{K_B}$ equals?
\begin{itemize}
\item[(1)] $20$
\item[(2)] $80$
\item[(3)] $1200$
\item[(4)] $3200$
\end{itemize}
\hfill \textit{Calculation Space}
%% Page 17
\textbf{Physics} \hfill \textbf{120-A} \hfill \textbf{Page 16}