A 1-in-diameter Stefan tube is used to measure the binary diffusion coefficient of water vapor in air at 80°F and 13.8 psia. The tube is partially filled with water with a distance from the water surface to the open end of the tube of 10 in. Dry air is blown over the open end of the tube so that water vapor rising to the top is removed immediately and the concentration of vapor at the top of the tube is zero. During 10 days of continuous operation at constant pressure and temperature, the amount of water that has evaporated is measured to be 0.0025 lbm. Determine the diffusion coefficient of water vapor in air at 80°F and 13.8 psia.