A tennis player strikes the tennis ball with her racket when the ball is at the uppermost point of its trajectory as shown. The horizontal velocity of the ball just before impact with the racket is v1 = 15 m/s and just after impact its velocity is v2 = 21 m/s directed at the 15∘ angle as shown. If the 60 g ball is in contact with the racket for 0.02 s, determine the magnitude of the average force R exerted by the racket on the ball. Also determine the angle β made by R with the horizontal.