I need help with a elastic collison problem ive tried and tried but cant seem to find a solution, so i figure i ask the smart kids.. Heres the question

2. Collisions between atomic particles are often perfectly elastic. In one such collision, a proton traveling to the right at 258 km/s collides head on with an alpha particle (a helium nucleus with mass 6.65x10^(-27)) intially at rest. Find the velocity of each particle after the collision. How much kinetic energy does the proton loose during the collision? Where does this energy go?