Answer question 1, 2, 3

Background: A college is using the elective system. Students first enter their student id and password to log in. After successful landing, the student can see their own related information: student id, class, and name. The student can then browse through the optional courses, view the courses he has chosen, and get a brief introduction to the courses that he interests Student's information is: student id, class, name and password (sid, class, sname, pass) Course information includes: course id, course name, course credit, course time, classroom, limited number of students, and course description (cid, cname, credit, ctime, place, amount, summary, kind). The courses are divided into two categories: Cultural Quality Courses and Public Elective Course Teacher's information includes: teacher id, name, and department (tid, tname, tplace) The school stipulates that the same teacher can open more than one course during a semester, but no repeat course can be offered, The same several different teachers and can be chosen by more than one student. A student can take multiple courses, but up to two courses of the same type can be selected Question: 1. Create an ER model to represent the elective system 2. Transfer the ER model to a relational model. 3. Create all tables in the relational model using DDL course can be opened by