Kathy is driving her 1000 kilogram car at 20 m/s and does not notice that I don't dump truck has stopped in front of her she rear ends the 3000 kilogram truck after the Collision Cathy bounces back at -10 m/s what is the final velocity of the dump truck
A. -20 m/s
B. -10 m/s
C. 10 m/s
D. 20 m/s