The vapoure pressure of benzene and toluene at `20^(circ)C` are `75 mm` of `Hg` and `22mm` of `Hg` respectively. `23.4g` of benzene and `64.4g` of toluene are mixed. If two forms ideal solution, calculate the mole fraction of benzene in vapour phase when vapour are in equilibrium with liquid mixture.