Well that is your
homework, so it is up to you.
Start with the first requirement: create the
file. If you don't know how to then study
format (see, for instance: "XML at w3c schools"
) and have a look at simple
file samples (you'll find tons of those, on the net).
You may use the same method to fulfill the other requirements.
By the way, if you have a specific question (suitable for Q&A) then feel free to ask us here.