Answer this clearly please with clear ERD diagram and explanation. A university registrar$$s office maintains data about the following entities: $($a$)$ courses, including number, title, credits, syllabus, and prerequisites; $($b$)$ course offerings, including course number, year, semester, section number, instructor$($s$),$ timings, and classroom; $($c$)$ students, including student$-$id$,$ name, and program; and $($d$)$ instructors, including identification number, name, department, and title. Instructors belong to a department. We store for each department: name, school, and the head of the department.

Furthermore, the enrollment of students in courses and grades awarded to students in each course they are enrolled in$.$

Construct an ERD diagram for the registrar$$s office. Document all assumptions that you make about the mapping constraints.