Here's the question you clicked on:
patbatE21
What is the minimum total energy released when an electron and its antiparticle annihilate each other?
the energy released when a particle and it's antiparticle annihilate each other = 2*(mass of the particle)*(square of speed of light) = 2m(c^2)
mass/energy of a electron/positron is about 0.511MeV
but to collide i guess the electron and positron would have some kinetic energy too