a helium balloon, with a combined mass of the balloon and helium of 20kg, is used to lift a payload of 70kg. At an altitude of 30 km the balloon stops and remains stationary. a. Explain b. at 30km, the density of air os 0.035kg/m^3. What is the volume of the balloon assuming that the volume of the payload is 0.010m^3 can someone plz help, i need to kinda have a idea for my quiz tomorrow for the vlume i came up with v=m/density v = 90/.035 v = 2571???