The envelope and basket of a hot-air balloon have a combined weight of 2.45 kN, and the envelope has a capacity (volume) of 2.18 x 103 m3. When it is fully inflated, what should be the temperature of the enclosed air to give the balloon alifting capacity (force) of 2.67 kN (in addition to the balloon"s weight)? Assume that the surrounding air, at20.0°C, has a weight per unit volume of 11.9 N/m3 and a molecular mass of 0.028 kg/mol, and is at a pressure of 1.0 atm.