A positron is a particle that has

the same mass but opposite charge of an electron. A

positron and an electron are initially very far apart

and travel toward each other with a certain initial

speed. Define the system to be the positron and elec$-$

tron. When they start very far from each other, each

particle has a kinetic energy of $41014$ J$.$

When they collide, they disintegrate and com$-$

pletely transform into two photons. What is

the total $($combined$)$ kinetic energy of the two

photons after the collision?