Consider the following relational schema. Enroll(SIN: Integer, CID: String, Term: String, Grade: Integer); Teaches(CID: String, Term: String, InstructorSIN: Integer); Note: in the above relations, "SIN" stands for Social Insurance Number, and thus is a unique identifier for any person associated with the university (whether student, instructor, or other employee of the university). Write SQL CHECK constraints, assertions or triggers (as appropriate) to ensure each of the following requirements, considered independently. a. [2 marks] All grades are between 0 and 100 (inclusive) b. [3 marks] No student can take more than 5 courses in a term