In the figure, block 2 (mass 1.10 kg) is at rest on a frictionless surface and touching the end of an unstretched spring of spring constant 231 N/m. The other end of the spring is fixed to a wall. Block 1 (mass 1.40 kg), traveling at speed v1 = 4.40 m/s, collides with block 2, and the two blocks stick together. When the blocks momentarily stop, by what distance is the spring compressed?