Two n-digit integers (leading zeros allowed) are considered equivalent if one is a rearrangement of the other.

Question:

Two n-digit integers (leading zeros allowed) are considered equivalent if one is a rearrangement of the other. (For example, 12033, 20331, and 01332 are considered equivalent five-digit integers.)
(a) How many five-digit integers are not equivalent?
(b) If the digits 1,3, and 7 can appear at most once, how many nonequivalent five-digit integers are there?