Solve the following in Java.

Question $11$: Understanding Class DesignWhy was it necessary to create an abstract class Person instead of directly defining Student and Lecturer classes?

Question $12$: Encapsulation and Access ModifiersWhy are the fields in the Person, Student, and Lecturer classes declared as private, and what are the benefits of using access modifiers in this scenario?

Question $13$: Constructor UsageExplain the role of constructors in the Student, Lecturer, and Course classes. How do they contribute to object initialization?

Question $14$: Polymorphism and InterfacesHow does the use of polymorphism enhance the design of the University Management System? Provide an example based on the scenario.

Question $15$: Method Implementation and OverridingThe displayInfo method is overridden in both Student and Lecturer classes. What is the significance of method overriding in this context?