An astronaut on a space walk is floating away from her space ship at a speed of 0.15 m/s. In order to change directions and move towards her ship, the astronaut turns on the jet pack she is wearing, which ejects some gas at a speed of 30 m/s. After turning off the jet pack, the mass of the astronaut and her pack is 120 kg and she is moving towards her ship at a speed of 0.24 m/s. What is the mass of the ejected gas?