Note: 2.5 * 10^3 kg = 2.5 * 10^3 * 10^3 = 2.5 * 10 ^6 g, Because 1 kg = 10^3 g
This is simple proportion
1.80 grams of air has a volume of 1 liter.
1 gram of air would have a volume of (1/1.8) liter
Therefore, 2.5 * 10^6 g would have: 2.5*10^6 * (1/1.8) = 1.3888 * 10^6 liters of air.
