Consider an 18-m-diameter hot-air balloon that, together with its cage, has a mass of 120 kg when empty. The air in the balloon, which is now carrying two 70 - kg people, is heated by propane burners at a location where the atmo spheric pressure and temperature are 93 kPa and 12oC, respectively. Determine the average temperature of the air in the balloon when the balloon first starts rising. What would your response be if the atmospheric air temperature were 25oC?