SOLUTION: In how many ways can a student org form a committee of 4 members from 3 freshmen, 4 sophomores, 9 juniors, and 4 seniors if each year level will be represented?

Notice that the problem has 4 (four) levels, and it requires that each and every level 
be presented in the committee of 4.


It means that from each level, exactly one representative can be and should be elected.


One representative of 3 freshmen   can be elected in 3 ways.

One representative of 4 sophomores can be elected in 4 ways.

One representative of 9 juniors    can be elected in 9 ways.

One representative of 4 seniors    can be elected in 4 ways.


Now, guided by the Fundamental counting principle, one may conclude that
the number of all possible different committees as described in the problem
is the product  3*4*9*4 = 432.    ANSWER