Write a letter to the librarian

Dear Librarian,
I am writing this letter to seek apology for the expected delay in the return of book which you issued me as per my request.
I am a first year student of applied psychology and my student number is PY23478. Last Thursday I borrowed a book from the library called “Change your brain, Change your life” written by Daniel Amen. The reason I borrowed the book was for my final year assignment and it helped me a lot.
Unfortunately, I got sick at the end of my assignment. I was so busy with my assignment and other projects that I couldn’t sleep properly for days, and this resulted in fever. Due to my serious medical condition, I was hospitalized for a week.
I am bound to pay any kind of fine imposed by the library, and I would happily pay. Moreover, if I can be of any assistance to library or any voluntary work, then I wouldn’t hesitate to do it. Lastly I would like to donate some of my books to library as a goodwill gesture.
Thank you for your co-operation in this matter.
Sincerely,
XYZ