Physics question dealing with momentum?

A 56.2 gram tennis ball is loaded into a 1.27 kg homemade cannon. The cannon is at rest when it is ignited. Immediately after the impulse of the explosion, a photogate timer measure the cannon to recoil backwards at a distance of 6.1 cm in 0.0218 seconds. Determine the post -explosion speed of the cannon and of the tennis ball.