The binding energy of an element is 64 MeV. If the binding energy per nucleon is 6.4 MeV, then the number of nucleons are 10.
The binding energy of deuteron (21H) is 1.15 MeV per nucleon and an alpha particle (42He) has a binding energy of 7.1 MeV per nucleon. Then in the reaction 21H+21H→42He+Q the energy Q released is