I am stuck on this question! A 10kg mass, M1, slides to the rght across a frictionless floor at v0=5m/s.

If anyone can help! I am stuck on this question!

A 10kg mass, M1, slides to the rght across a frictionless floor at v0=5m/s. It impacts a massless spring of length 1m, with k = 250N/m attached to another 10kg mass, M2. M1 sticks to the spring, which is stuck to M2, and the whole system goes moving along.