The binding energy per nucleon of deuterium and helium atom is 1.1 MeV and 7.0 MeV. If two deuterium nuclei fuse to form helium atom, the energy released is

1H2+1H2→2He4+ energy   Binding energy of a  1H2 deuterium nuclei  =2×1.1=2.2MeV Total binding energy of two deuterium nuclei =2.2×2=4.4MeV  Binding energy of a  2He4 nuclei =4×7=28MeV  So, energy released in fusion =28−4.4=23.6MeV