A ball of rest m0= 1kg moves along the x-axis at speed v = 0.99c and collides elastically with a similar ball at rest in the lab frame. The?

Question

A bowling ball of rest mass m0 = 1 kg moves along the x-axis at speed v = 0.99c and collides elastically with a similar bowling ball at rest in the lab frame. The second ball now moves along the x-axis. In the lab frame, what is the combined kinetic energy of the balls after the collision?