At 80 deg. Celsius the vapor pressures of pure liquids X, Y, and Z are 385, 190, and 66 mm Hg, respectively.

At 80 deg. Celsius the vapor pressures of pure liquids X, Y, and Z are 385, 190, and 66 mm Hg, respectively. What pressure must be exerted on the surface of the solution containing one mole of X, three moles of Y, and two moles of Z for boiling to begin at 80 deg. Celsius?