Worth 20 points Please answer and show work with the conversion:

A car moving with a velocity of 30m/s has a constant acceleration of -4m/s? What will be the velocity 3 seconds later?
A) -12m/s
B) 18m/s
C) 42m/s
D) 90m/s

Arailroad car collides with and sticks to an identical railroad car that is initially at rest. after the collision, the total kinetic energy of the two cars is a) the same as before. b) half as much as before. c) one third as much as before. d) one fourth as much as before. e) twice as much as before.