1. The problem statement, all variables and given/known data Consider the combination of an electron with positron(I) and an electron with proton(II).The possible processes are: (i)formation in positronium in (I) (ii)formation in Hydrogen ataom in (II) (iii)annihilation of each other and gamma emission in (I) and (II) both (iv)elastic scatterinh in (I) and (II) both 2. Relevant equations 3. The attempt at a solution I think all but (iv) may be correct---elastic scattering should not happen... Please check.