Good day @fendit, i really appreciate your ability to fish out this error. It shows your dedication to this academy. However, i apologize for not adding the references. I really had it in mind but it skipped my mind as at the time I finished the homework. The references are still where I kept them when I was doing my home work. You can see I added the references for the other ones. I have added the references to my homework. Please oblige, kindly revisit my work as I am really dedicated and worked hard to do this homework. Thank you.