Suppose you loft a ball in a tennis game with an initial speed of 16.5 m/s at an angle of 52.0 degrees above the horizontal. At this instant your opponent is 10.0 m away from the ball. He begins moving away from you .3 s later and hopes to reach the ball and hit it back at the moment that it is 2.10 m above its launch point. With what minimum average speed must he move?