In Fig. $9-80$, block 1 of mass $m_{1}=6.6 \mathrm{~kg}$ is at rest on a long frictionless table that is up against a wall. Block 2 of mass $m_{2}$ is placed between block 1 and the wall and sent sliding to the left, toward block 1 , with constant speed $v_{2 j}$. Find the value of $m_{2}$ for which both blocks move with the same velocity after block 2 has collided once with block 1 and once with the wall. Assume all collisions are elastic (the collision with the wall does not change the speed of block 2).