A tennis ball is dropped on the floor from a height of 20 m. It rebounds to a height of 5 m. The ball was in contact with the floor for 0.01s. What was its average acceleration during the contact? (g=10 m/s²)
A. −3000m/s²
B. −2000m/s²
C. −1000m/s²
D. 500m/s²