The vapour pressure of a solvent is found to be $400 mm$ Hg at $300 K$ When a certain amount of nonvolatile solute added to $50\;mol$ of the solvent its vapour pressure decreases to $360\;mm Hg$. The amount of solute added is:

Question

$\begin{array}{1 1} 2.41 \;mol \\3.42 \; mol \\4.54\;mol\\5.45\; mol\end{array} $