Please answer question 2 a, b and c. Thank you.

(8 marks) 2. A relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as invented by E. F. Codd. a) Explain referential integrity features that a relational database management system must provide with example. (4 marks) b) Briefly explain enterprise constraint in relational model with example, (4 marks) c) Illustrate the Database System environment with suitable diagrams (12 marks)