1. 6 pts -- 3 pts for new-item!
                  changing: should use set-item-...!
                            (or whatever they call their structures)
                  adding:   should use set! to global list 
            1.5 pts for inflate!
                  should use set-item-price! (or whatever they call their 
                  structures)
                  should preferably use for-each, but don't expect it
            1.5 pts for discontinued!
                  should use set! to global list

2. 4 pts -- 2 pts for init!
            2 pts for next!

            Changing the internal representation correctly is almost trivial, 
            so this is mostly about initializing and updating the drawing
            correctly.