### Conservation of momentum and energy: A 0.420 kg ice puck, moving east with a speed of 3.04 m/s...

A 0.420 kg ice puck, moving east with a speed of 3.04 m/s, has a head-on collision with a 0.930 kg puck initially at rest. Assuming a perfectly elastic collision, what is the speed of the lighter puck? Use east as the positive axis.