Question 10
The diagram below shows a $6\times6$ box. Balls A to L enter along columns and exit along rows. The point of entry and the point of exit of each ball are marked by its own letter. Reflectors may be placed along either diagonal of any square in the box, four of which are shown as an illustration. When a ball hits a reflector, it bounces off in a perpendicular direction. You must make every ball go to the right place, as illustrated by the balls B and K. You must remove the four reflectors used in the illustration, and then place ten reflectors in other squares. You may not put any reflector in the same position as in the illustration.
