13b. Write the SQL command necessary to create table CLASS.
CREATE TABLE class
( classID CHAR (10),
profID CHAR (10),
courseID CHAR (10),
studentID CHAR (10),
semester CHAR (30),
PRIMARY KEY classID,
FOREIGN KEY profID REFERENCES professor (profID),
FOREIGN KEY courseID REFERENCES course (courseID),
FOREIGN KEY studentID REFERENCES student (studentID) );