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
balloon can lift up. The density of hot air is about 0.25 kg per cubic meter less than
that of cool air, which means a cubic meter of hot air can lift about 0.25 kg. What is
the minimum volume of hot air (in cubic meters) needed to lift a hot air balloon,
which weighs 375 kg and is carrying 3 people who weigh at least 68 kilograms each?
Enter the number only.