I am not sure but this is my best guess.
Forget about Henry, there are 11 people which are to be divided into groups of 3,3, and 5
There are 11C5 ways to choose the group of 5
Now there are 6C3 ways to choose a group of 3 BUT this is double counting, I need to divide by 2
so I have 11C5 * (6C3 /2)
Now there are 2 options for where to put Henry.
so I now have 11C5 * (6C3 /2) * 2 = 462*20/2*2 = 9240 option.