A small toy school bus rear-ends a big toy school bus initially at rest. The bigger bus is several times heavier than the smaller one.
Which of the following statements are true if the collision is totally inelastic?

a) The two busses continue together at the same speed.
b) Mechanical energy is conserved.
c) The small bus exerts the same amount of force on the big bus as vice versa.
d) Momentum is conserved.
e) The small bus will go backwards.