I think that Problem 3 is very unclear.  I couldn't figure out what it
was asking, and then even when I looked at the solutions, it took me a
while.  I guess you just want to find the set of states that you can
get to from some common state, but I don't see how you can figure this
out from the question.  Also, in the hw the motivation for their
learning state machines was to prove termination, and this doesn't
have anything to do with that.  But mainly my problem is just that I
caouldn't figure out what the problem was asking.

Problem 9 was also a little confusing.  Maybe I am being silly, but it
isn't clear that the invited people come to the party the next day.
It would be clearer if you said that 5 people _attend_ on the first
day, and on the next day each of those people brings 2 people with
them, etc.  I didn't figure out the answer correctly here.

Problem 10 seems tedious (the first solution) and might be very
difficult to grade :), but it is okay.  My main concerns are the ones
mentioned above.

Alantha