Block A in (Figure 1) has mass 1.20 kg , and block B has mass 2.90 kg . The blocks are forced together, compressing a spring S between them; then the system is released from rest on a level, frictionless surface. The spring, which has negligible mass, is not fastened to either block and drops to the surface after it has expanded. Block B acquires a speed of 1.45 m/s . What is the final speed of block A? How much potential energy was stored in the compressed spring?