HW3 grading.

15 points total

0 points if no hw3.txt file in your ~/handin/ directory.

5 points for having a scratch project that does /something/.

10-12 points for a project that shows it's on the right track,
but doesn't come up with an answer due to a logical error.

"Extra" - at most 2 extra credit points for doing the extra 
items.