2) Suppose we are to design a registrar's database to store information about students, courses, the courses students have taken, and the grades students have gotten in these courses. Courses have a number, a department, and title, for example,"CS101: Introduction to computing "has Department-CS, number-101, and title "Introduction to Computing. "Numbers are assigned by departments and different departments may use the same number. Students are represented by their (unique) student ID and their name. "Enrollments" each consists of a course, a student who took that course, and the grade the student got in the course. Draw an ER model and clearly explain your rationale