Permutations and Combinations

I'm currently having a bit of trouble with some questions, this one in particular. Everytime I try and do it I end up doing some sort of statistic probability, which is not what I need. The question is:

Suppose that a die is tossed ten times and the sequence of upturned numbers is recorded in order

a) How many outcomes are there?

b) How many outcomes are there exactly 3 fours?

c) How many outcomes are there at most 3 fours?

What I have done so far is figured out that there would be 6^10 different possible outcomes, but apart from that I keep going in a loop for b and c. Any help would be appreciated, or any pointers into what I should be looking at doing. :)