1. The problem statement, all variables and given/known data Given that 1,206,900 liters of oxygen are required for a round-the-world trip for a hot-air ballon with a crew of three, and given that carbon-fiber wrapped bottles have a maximum pressure of approx 4500 psi, what total volume of pressure vessel would be necessary to bring along adequate compressed air for the flight? If the bottles come in volumes of 12ft^3, how many bottles does this represent? The ballon flies at an altitude of 40,000 feet. Find these values for 40,000 ft and 0 ft (sea level.) 2. Relevant equations This question comes accross as a standard Chemistry conversion. Air weighs 1.3 grams per liter. 1 psi is equal to .0703 Kg/cm, so 4500 psi equals 316.38 kg/cm. 3. The attempt at a solution The question seems to be asking me to convert liters to psi, but I can't figure out how to do that, even when I try converting liter to kg/cm.