An insulated glass tube and condenser are mounted on a reboiler containing benzene and toluene. The condenser returns liquid reflux so that it runs down the wall of the tube. At one point in the tube the temperature is 170oF, the vapor contains 30 mol% toluene, and the liquid reflux contains 40 mol% toluene. The effective thickness of the stagnant vapor film is estimated to be 0.1 in. The molar latent heats of benzene and toluene are equal. Calculate the rate at which toluene and benzene are being interchanged by equimolar countercurrent diffusion at this point in the tube in lbmol/h-ft2. Diffusivity of toluene in benzene = 0.2 ft2/h. Pressure = 1 atm total pressure (in the tube).Vapor pressure of toluene at 170°F = 400 torr.