Two lighter nuclei combine to form a comparatively heavier nucleus by the relation given below: $$ { }_1^2 \mathrm{X}+{ }_1^2 \mathrm{X}={ }_2^4 \mathrm{Y} $$ The binding energies per nucleon ${ }_1^2 \mathrm{X}$ and ${ }_2^4 \mathrm{Y}$ are 1.1 MeV and 7.6 MeV respectively. The energy released in this process is . MeV.