A plastic bag is filled with helium at atmospheric pressure and 18.0 oC. Assume that the mass of the bag is negligible and take the temperature of the outside air to be 0 oC. With the help of this "balloon" we want to lift a 50.0 kg girl off her feet. How large a volume of helium (in m3) is required? B)If hot air is used instead of helium, what is the required volume of the balloon if the air inside can be maintained at 39.0 oC ?