A thin block of soft wood with a mass of 0.0720 kg rests on a horizontal frictionless surface. A bullet with a mass of 4.67 g is fired with a speed of 556 m/s at a block of wood and passes completely through it. The speed of the block is 18.0 m/s immediately after the bullet exits the block. (a) Determine the speed of the bullet as it exits the block.