site a specific problem that this project can solve: Power Saving Device?

Question

It controls 4 electric fans which depend on the number of people inside a room, very useful in a classroom. It also has a timer to set how many hours the room will be used.

Answer 1

Anytime you can save energy, you will lower the cost of operation and this will create funds which can be used for other activities.

Question: If this system is sophisticated enough to "know" how many people are in the room, why would it need a timer?