2. Explain the difference between a weak entity and a strong entity in a mandatory relationship. Use the scenario: A car may have many insurance policies over the years. An insurance policy exists for year for a particular car. Cars are uniquely identified by a license plate number where as insurance policies are identified a sequential number for each car. 3. Explain what is meant by a specialization / generalization relationship. Illustrate this term in the following scenario The Accounting department in a company keeps the information about its employees in a database. The employees are classified as part-time employees, full-time employees, and interns. Interns are usually students who work with the company during the summers. Complete the E-R diagram below by: a). Adding a unique attribute (relationship) for each entity subtype b). Adding an attribute shared by all entities c). Identifying whether the disjoint or overlap rule applies d). Identifying whether the total specialization or partial specialization rule applies 4. Discuss how and when aggregates are used. a. When are they introduced on our diagram? b. How many relationships are allowed in an aggregate? c. What is the difference between a many to many relationship with attributes on our diagram vs an aggregate? Give examples d. Illustrate the following scenario. Final year undergraduate students are required to undertake a capstone research project. Each project is proposed by one or more lecturers and each student undertaking a project has to be supervised by a lecturer however not every lecturer supervises a project though he/she may propose one. Of course the grade a student received for a project needs to be recorded along with the academic year undertaken