A 5 g bullet moving with an initial speed of vi=400 m/s is fired into and passes through a 1 kg block as shown in figure.The block,initally at rest on a frictionless,horizontal surface,is connected to a spring with forcr constan 900 N/m.The block moves d=5 cm to the right after impact before being brought to rest by the spring.Find the speed vf ar which the bullet emerges from the block.