A block of mass m= 2.40 kg starts from the rest and slides down a 30.0 incline which is 3.60 mhigh. At the bottom, it strikes a block of mass M= 6.40 kg which is at rest on a horizontal surface. (Assume a smooth transition at the bottom of the incline.) The collision is elastic, and friction can be ignored.

(a) the speed of the block with mass m= 2.40 kg after the collision.

(b) the speed of the block with mass M = 6.40 kg after the collision.

(c) what distance along the incline will the smaller mass climb back after the collision.

I need to know what equation to use and how to use it so I can work out a problem on the paper and show my work.