How do you calculate impulse?

Recent studies have raised concern about `heading' in youth soccer (i.e., hitting the ball with the head). A soccer player `heads' a size 4 ball deflecting it by 40.0�, and keeps its speed of 16.70 m/s constant. A size 4 ball has a mass of approximately 2.000 kg. What is the magnitude of the impulse which the player must impart to the ball?