A 0.276-kg volleyball approaches a player horizontally with a speed of 15.2 m/s. The player strikes the ball with her fist and causes the ball to move in the opposite direction with a speed of 21.4 m/s.

(a) What impulse is delivered to the ball by the player? (Take the direction of final velocity to be the positive direction. Indicate the direction with the sign of your answer.)__________kg · m/s
(b) If the player's fist is in contact with the ball for 0.0600 s, find the magnitude of the average force exerted on the player's fist. __________N