I have a question about lift power of some gases, cos when the teacher was explaining it to me I wasn't paying much attention

:

The volume of the aeorostat is 100,8 m

^{3}. The mass of the balloonist is 70 kg, the mass of gondola and aerostat is 40 kg. Count, which aerostat from the following picture won't be able to lift the balloonist.

And so there's a picture of three aerostats, and on each of them there is written H

_{2}, He, CH

_{4}