A fish at a depth of 30 m is neutrally buoyant. The fish rises to the surface, adjusting the amount of air in its air bladder so that it remains neutrally buoyant. What fraction of the original number of air molecules that were in the air bladder remains when the fish is at the surface? Assume that the density of water is 1 g/cm3, air behaves as an ideal gas, and that the temperature is constant. The density of the fish's body outside of the air bladder is 1.067 g/cm3, and the density of air in the air bladder is essentially zero.