Please explain this problem.

Consider a function f: X -> Y

1. How many different functions can we create if the only requirement is that the function is well-defined? Come up with a formula using n = |X| and k = |Y|.
2. How many different functions can we create if the function is 1-1? Come up with a formula using n = |X| and k = |Y|.
3. How many different functions can we create if the function is must be a bijection? Come up with a formula using n = |X| and k = |Y|.