Explain how we can use a flow network to solve the following problem:

We have nn students and cc classes. Each class has a max enrollment of e$1,$e$2,...,$ece$1,$e$2,...,$ec$.$ Each student can take up to $5$ courses. Furthermore, some of the classes are designated as senior electives, and a student is not permitted to take more than $3$ senior electives in one semester.

How can we determine the maximum possible overall class enrollment in a semester subject to all of these constraints?