HATS

Here is a brain teaser that was given to us in training. Please let me know how well you did in guesing the correct answer! (Please provide an explanation and time it took). Have fun!

Rules:

1. A, B, C & D are standing on a straight line.

2. A is facing right and could only see the wall.

3. B is facing left and could only see the wall.

4. C is facing left and could only see B and the wall.

5. D is facing left and could only see C, B and the wall.

6. They are all wearing hats.

7. They know there are only 4 hats, 2 black and 2 white.

8. They are to be executed.

9. If one of them would be able to shout out the color of hat he is wearing, they would be freed.

10. If they shout the wrong color, they would all be killed mercilessly.

11. They could not move their heads, nor could they talk with each other.

How do they all get away?