A proton colliding with a stationary carbon nucleus

[HandcuffedKitty]

A proton of mass m undergoes a head-on elastic collision with a stationary carbon nucleus of mass 12m. The velocity of the proton is 395 m/s in the positive x direction. The velocity of the center of mass of the system is 30.38 m/s.

What is the velocity of the proton after the collision?????

[turin]

"Head-on" tells you the angle. "Elastic" tells you that KE is conserved.