The Red Bull team made a world record of a free-fall jump in 2014. The team used a balloon filled with helium (He) to get to the altitude. This question concerns the state of the balloon at 10 km altitude. Consider the pressure and temperature of the helium to be equal to those of the surrounding air (pH = Pair and The = Tair) as shown in the figure below. Pair PHe at all times Air Pair, Pair Tair Helium , , Assume that both air and helium behave as ideal, perfect gasses. The molar mass of helium is 2 kg/kmol and the molar mass of air is 28.97 kg/kmol. a. What is the density of the helium at 10 km altitude? b. The buoyancy force F, acting on a body equals the weight of the displaced fluid: Fb Pair Vballoong If the payload mass for this balloon is 70 kg, what is the minimum amount of helium needed for the balloon to float at 10kg 10 km altitude? Consider the force balance on the balloon.