Answer:
This assignment can be made in 1365 ways.
Explanation:
The order in which the shifts are assigned is not important. For example, employees A, B, C, D and D,C,B,A being assigned is the same thing. So, we use the combinations formula to solve this question.
Combinations Formula:
is the number of different combinations of x objects from a set of n elements, given by the following formula.

In this question:
Assignment of 4 employees, from a set of 15. So
