A University has a new video camera system. Suppose you want to design an application that needs to have an object (central monitor in the Security Center) that is notified when people are coming close to the sensor (e.g., if someone is in the range of 30 ft, then the camera starts recording otherwise not).

Which is the design pattern proper to be used in this case?

Explain why this is the proper design pattern.

Write a simple Java code which respects this requirement.