Dealing with multiple sets

[John Henry]

Hi list,

If I have a bunch of sets:

a = set((1, 2, 3))
b = set((2, 3))
c = set((1, 3))
....

What's the cleanest way to say:

1) Give me a list of the items that are in all of the sets? (3 in the
above example)
2) Give me a list of the items that are not in all of the sets? (1,2 in
the above example)

Thanks,