Let U denote the set of all 5 digit integers. (Note 01466 is not a 5 digit integer) a) Find n(U) answer= 90,000 b) Let A be the set of integers in U...

Let U denote the set of all 5 digit integers. (Note 01466 is not a 5 digit integer)

a) Find n(U) answer= 90,000

b) Let A be the set of integers in U that have 5 distinct digits. The integers 24357 is an example of an element of A. Find n(A) answer= 27,216

c) Let B be the set of integers in U that only have odd digits. Find (B). answer= 3125

Please help I have never seen this type of question before.