This question is examining your understanding of the binding energy in the nucleus and its connection to the mass defect.
The energy released in step X is given in the body of the question, 1.20 MeV
For a 3-mark question, the marking scheme would probably be: 1 mark for proposing a valid reason why step Y releases more energy than step X, 1 mark for using the correct mass defect calculation, and 1 mark for knowing how to relate joules to electron-Volts and get the correct numerical comparison.