Solutions of benzene and toluene obey Raoult's law. The vapor pressures at 20°C are: benzene, 76 torr; toluene, 21 torr. If the mole fraction of benzene in a particular benzene-toluene solution is 0.63, what is the mole fraction of benzene in the vapor phase in equilibrium with that solution? Select one: a. 0.78 b. 0.49 c. 0.63 d. 0.86 e. 0.24