Question about Spring compression

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Show your work and the equations that you used.

A block of mass slides along a frictionless table with a speed of 10 m/s. Directly in front of it, and moving in the same direction, is a block of mass moving at 3.0m/s. A massless spring with spring constant is attached to the near side of (the side facing ). When the blocks collide, what is the maximum compression of the spring? (Hint: At the moment of maximum compression of the spring, the two blocks move as one. Find the velocity by noting that the collision is completely inelastic at this point.)