p1:
"pinpoint exactly" is a bit vague.
Do you want something like "induction step is wrong"
or 
the step from n=1->2 is not true.
Maybe slightly rephrase what you are asking for.

p3:
how do people get partial credit on part a?
part b can be answered using intuition too (1/2 and 1/2 eventually).
Is that answer accepted?

p4:
part c might be a pain to grade. I don't think it is necessary.
give more points to b. If they get inc-excl then they get it right
anyway. If not, in order to get it right, they will waste a lot of time.

p5:
part b typo: in how many (ways) can you ...

p6: isn't that a pset problem?
part (c): You "may" express...
Is that in case they don't get part b? Otherwise, it might confuse them.

p7: I think part b deserves more points, since they need to find the 
indicators and so on...

p9: I don't know why we have this problem there. What are we testing with
this one?

I am looking now at the rest. I will put a no.2 file as soon as I am done.

nikos