An electron and a positron have masses of 9.11 10-31 kg. They collide and both vanish,

Question:

An electron and a positron have masses of 9.11 × 10-31 kg. They collide and both vanish, with only electromagnetic radiation appearing after the collision. If each particle is moving at a speed of 0.20c relative to the laboratory before the collision, determine the energy of the electromagnetic radiation.