Create an ERD using Chen's notation.

"I'm the manager of a training company that provides instructor-led courses in management techniques. We teach many courses, each of which has a code, a name, and a fee. Popular courses are Introduction to Network Security, Introduction to UNIX, Foundations of Algorithms, Software Project Management, XML: Technology and Applications, Foundations of Computer Architecture, and Introduction to TCP/IP. Courses vary in length from one day to five days. An instructor can teach several courses. New courses may be added based on students' requests or instructors' suggestions. Each course is taught by only one instructor. We create a course and then line up an instructor. We track each instructor's name and phone number. The students can take several courses over time, and many of them do this. We track each student's name and phone number. Some of our students and instructors do not give us their phone numbers."