Mole fraction of the benzene in the vapour phase which is in equilibrium with a solution of benzene $(p^0=120torr)$ and toluene$(p^0=80torr)$ having 4.0mole of benzene and 6 mole of toluene in solution.

Question

$\begin{array}{1 1}(a)\;0.50\\(b)\;0.40\\(c)\;0.30\\(d)\;0.20\end{array}$