7) The heat from students, from lights, through the walls, and so forth to the air moving through a classroom is 18000 kJ/hr. Air is supplied to the room from the air conditioner at 17C. The air leaves the room at 27C. Determine the following: (a) Air mass flow rate (kg/s), (b) Air volumetric flow rate m3/hr at inlet conditions (c) Duct diameter (m) for an air velocity of 3 m/s.