Consider the following relations.

Students $($StudentID$,$ First Name, Last Name, Age$)$

Courses $($CourseID$,$ CourseName, Instructor, Credits$)$

Enrollments $($EnrollmentID$,$ StudentID, CourseID$)$

Write relational algebra expressions for the following. You can separate your answers by numbering them.

$1.)$ Retrieve the First Names and Last Names of students who are older than $20$ years old.

$2.)$ Write a relational algebra expression to retrieve the CourseName and Instructor of courses that have more than $3$ credits.

$3.)$ Retrieve the StudentID, First Name, Last Name, and CourseName of students enrolled in courses where the course creditsare greater than $3.$