There are 19 people total, and groups of four are being asked of us. We can use the formula for permutations or combinations.
Permutations:

Combinations:

Where in both scenarios, there are
n objects being chosen at
r times.
19 P 4 is 93024
19 C 4 is 3876
It all depends on whether order matters with group placement; if it does, your answer is
93024, if not, then your answer is
3876.:)