6.7 A fan draws air from the atmosphere through a 0.30-m- diameter round duct that has a smoothly rounded entrance. A differential manometer connected to an opening in the wall of the duct shows a vacuum pressure of 2.5 cm of water. The density of air is 1.22 kg/m. Determine the volume rate of air flow in the duct in cubic feet per second. What is the horsepower output of the fan? Fan 0.30 m 2.5 cm