There is 5mm deep water at 20C in the 20mm diameter stefan tube. The total pressure is 91.19kPa and the environment is dry air. Just above the water level is covered with a stagnant air film, the thickness of the air film is 15mm. The concentration of water on the surface of the still air film is negligible. Since the vapor pressure of water at 20C is PA=2.33kPa and the diffusion coefficient at 25.9C and 101.325kPa conditions is 0.258cm2/s; Calculate: a) The evaporation flux of water, b) How much water will evaporate after 15 minutes