Art Portfolio for Architecture?

For university application, I need to mail the university an Art Portfolio together with my application form, for admission into the Architecture Faculty.
I’m absolutely clueless on what to do.

Around how many pieces will I need?
Must they all be completed, or will undone plans and sketches do?
Do I submit original master copies, or pictures? Or scans of images? I mean, if I’m applying to a few universities, I need duplicates.
God.