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