How would I fix my SQL coding of integrity constraints? (Also, don't change the name of the constraints if you can)

Here's my code:

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SPOOL ddl.out SET ECHO ON /* Homework: SQL/DDL Author: */ -- -------------------------------------------------------------------- DROP TABLE Students; -- CREATE TABLE Students ( id INTEGER, name CHAR(10) NOT NULL, classification CHAR(10) NOT NULL, hours INTEGER, gpa NUMBER(3,2) NOT NULL, mentor INTEGER, -- -- IMPORTANT: use the names IC1, IC2, IC3, IC4, and IC5 as given below. -- IC1: -- Student Id is the primary key <<< your SQL code goes here>>> -- IC2: -- Every student must be classified as 'freshman', 'sophomore', -- 'junior', or 'senior' <<< your SQL code goes here>>> -- IC3: The gpa must be between 0 and 4.0 (inclusive). <<< your SQL code goes here>>> -- IC4: -- To be classified as a 'junior',a student must have -- completed between 55 and 84 hours (inclusive). <<< your SQL code goes here>>> -- IC5: -- Every mentor must be a student, and -- A student may or may not have a mentor, and -- If a mentor's row is deleted, then his/her students are -- left without a mentor, and -- Defer the spec of this IC so that a students record can be -- inserted before his/her mentors record is inserted. <<< your SQL code goes here>>> ); -- ------------------------------------------------------------------ -- TESTING THE SCHEMA -- ------------------------------------------------------------------ -- Beginning of Transaction-1 (consisting of the next 5 INSERTs) SET AUTOCOMMIT OFF INSERT INTO Students VALUES (10, 'Joe', 'freshman', 15,2.8, 20); INSERT INTO Students VALUES (20, 'Joyce', 'sophomore', 35, 3.7, 30); INSERT INTO Students VALUES (30, 'Lisa', 'junior', 63, 3.5, 40); INSERT INTO Students VALUES (40, 'George', 'senior', 82, 3.7, null); INSERT INTO Students VALUES (50, 'Kim', 'junior', 54, 3.5, 40); COMMIT; -- End of Transaction-1 SELECT * FROM Students; -- ------------------------------------------------------------------- -- Now treat every one of the following INSERTs as a transaction by itself. h04-DDL.doc Page 3 of 3 SET AUTOCOMMIT ON INSERT INTO Students VALUES (20, 'John', 'freshman', 10, 3.5, 30); INSERT INTO Students VALUES (null, 'nobody', 'freshman', 10, 3.5, 30); INSERT INTO Students VALUES (60, null, 'freshman', 10, 3.5, 30); INSERT INTO Students VALUES (62, 'Bob', 'Senior', 82, 3.7, null); INSERT INTO Students VALUES (63, 'Allen', 'freshman', 10, 4.2, 30); INSERT INTO Students VALUES (64, 'May', 'junior', 43, 3.7, 40); INSERT INTO Students VALUES (74, 'Drew', 'junior', 85, 3.7, 40); INSERT INTO Students VALUES (75, 'Jane', 'sophomore', 39, 3.9, 70); INSERT INTO Students VALUES (41, 'David', 'senior', 93, 3.9, 40); -- -------------------------------------------------------------------- COMMIT; -- Inspect the table SELECT * From Students; -- DELETE FROM Students WHERE id = 40; SELECT * From Students; -- SET ECHO OFF SPOOL OFF