5) Hot air is less dense than cool air, so hot air will rise above cool air. Increasing the air temperature inside a hot air balloon makes it lighter than the surrounding air, so the bal-
loon can lift up. The density of hot air is about 0.25 kg/m 3 less than that of cool air,
which means a cubic meter of hot air can lift 0.25kg. What is the minimum volume of hot
air needed to list a hot air balloon carrying 800 kg?
a) 200 m3
b) 3200 m3
c) 1600 m3
d) 400 m