A balloon is to be filled with helium (density 0.178 kg/m^3) while the air outside has density 1.29kg/m^3.

A balloon is to be filled with helium (density 0.178 kg/m^3) while the air outside has density 1.29kg/m^3. the mass of the empty balloon is 80kg and it is to lift a load of 240kgwhat minimum volume is necessary for the lift off? assume that the balloon material and the load occupy negligible volumes.