For part (a) I just followed an example in the book and said the answer was 10 choose 3, is this right? I wasn't quite sure how to start part (b). --Rhollowe 16:46, 4 February 2009 (UTC)

For part b), can we just consider the cases when 0s are exactly 6,7,8,9,10 and add up those numbers?
I don't see any problem... --Lee 18:02, 4 February 2009 (UTC)

I believe you both are correct. and using the same logic Lee explained, you can find the answers to c and d ---Kristen 19:46, 4 February 2009 (UTC)