16c4*12c4*8c4*4c4 are the total no. of ways we can form 4 distinct groups of 4 people from 16 ppl.
once we have formed 4 groups in any of the one ways we can choose all 4 in only one way. since we have total no. of ways=16c4*12c4*8c4*4c4 so we can choose in the same no. of ways i.e 16c4*12c4*8c4*4c4.
plz correct me if wrong!!