\textbf{161.} A uniform rope of mass $40\,\text{kg}$, as shown in the figure below, rests against a frictionless wall. If the wall exerts a force of $300\,\text{N}$ on the rope, how many newtons does the surface exert horizontally on the rope?
$$\left(g = 10\,\frac{\text{N}}{\text{kg}}\right)$$
\textit{[Figure: A rope leaning against a wall at an angle, with the base on a horizontal surface]}
\begin{itemize}
\item[(1)] $400$
\item[(2)] $500$
\item[(3)] $600$
\item[(4)] $250\sqrt{3}$
\end{itemize}
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