Given that the energy released in the fusion of two deuterons to a ³He and a neutron is 3.3 MeV, and in the fusion to tritium and a proton it is 4.0 MeV, calculate the energy change for the process ³He + ¹n → ³H + ¹p. Suggest an explanation for why this process occurs at much lower temperatures than either of the first two.