There are 19 people total, and groups of four are being asked of us. We can use the formula for permutations or combinations.
Permutations: [tex] \frac{n!}{(n-r)!} [/tex]
Combinations: [tex] \frac{n!}{r!(n-r)!} [/tex]
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.
:)