Conservation of energy in elastic collision

[okgo]

Homework Statement

http://www.screencast.com/users/ntrinh3/folders/Jing/media/a4165a56-de0d-4a4a-a01e-49242fd505c4
Need help with question 13

Homework Equations

Conservation of energy and momentum occurs in elastic collision

The Attempt at a Solution

Why would the block 2 have an increase in energy? The velocity of block 2 will now be positive instead of negative but velocity is squared anyway.
The computer's answer was A. Increase, but shouldn't it remain the same?

 

[Pengwuino]

Imagine the situation here. A much much heavier object slams into an object with comparable (actually, the same!) speeds. What do you expect the smaller object to do?