Two blocks lie side by side on a frictionless table. The block on the left is of

Question:

Two blocks lie side by side on a frictionless table. The block on the left is of mass m; the one on the right is of mass 2m. The block on the right is pushed to the left with a force of magnitude F, pushing the other block in turn. What force does the block on the left exert on the block to its right?