A hot air balloon has a volume of 2.00 × 103 m3 when fully inflated, and the air inside the balloon is always at atmospheric pressure of 1.01 × 105 Pa because of the large opening used to fill the balloon and heat the air inside it. What is the mass of hot air inside the balloon if its temperature is 120°C? The universal gas constant is 8.314 J/mol K. (Assume a molecular weight of 28.8 g/mol for air.) please explain how to do this w/ formulas.