To solve Exercise 1, there are C(9,2) ways to choose two people for the group of size 2. Next, there remain 7 people, and hence C(7,3) ways to choose three people for the group of size 3. Finally, the last four people form a group of 4 by default. The total is C(9,2)*C(7,3) = 36*35 = 1,260.