A ping pong pall that is thrown at a velocity of 10m/s at an angle of 30 degrees to the horizontal hits a vertical wall while it is at the peak of it's height, and returns from the wall horizontally. As a result of hitting the wall, the ball loses 20% of its kinetic energy.

Find:
A. The height of the wall
B. The velocity of the ball when it hits the wall
C. The velocity of the ball after it's collision with the wall

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