A ball is dropped on to the floor from a height of 10 m. It rebounds to a height of 2.5 m. If the ball is in contact with the floor for 0.01 seconds, what is the average acceleration during contact?
(A) 1400 m/s2
(B) 2100 m/s2
(C) 700 m/s2
(D) 2800
m/s2.