Determine the speed of the proton after the collision

Question

A proton of mass moving with a speed of 2.1×10⁶ experiences a head-on elastic collision with an alpha particle of mass that is initially at rest.

Part A: Determine the speed of the proton after the collision? Deduce answer in two significant figures

Part B: Determine the direction of the proton's velocity following the collision?

i) The similar as the initial proton's velocity
ii) Opposite to the initial proton's velocity

Part C: Determine the speed of the alpha particle after the collision? Deduce answer in two significant figures.

Part D: Determine the direction of the alpha particle's velocity following the collision?