Two ice hockey pucks of different masses are on a flat, horizontal hockey rink. The puck #1 has a mass of 20 grams, and is motionless; the puck #2 has a mass of 12 grams, and is moving at 5.0 m/s to the left. It collides with the motionless puck #1. If the collision is perfectly elastic.

A: Set up equations due to conservation laws of linear momentum and energy.

B: What are the final velocities of the two pucks?