Hi,
I know from conservation of energy that ##E_i = E_f##
Thus, ## M_h c^2 + binding energy = M_{he}c^2+ M_e c^2 + K = M_{he}c^2 + 0.5 MeV + 0.0186 MeV##
If I'm right I have to find ##M_{he}c^2##, but something is missing in my understanding, since I don't see how to find that mass energy...