Dear Jquery.com users, 

I'm a noob in jquery and need some help with figuring out a few tricks regarding drag and drop scripts. Recently, I found "Drag and Drop shopping cart" tutorial. I downloaded the source code but the implementation lacks some functionality. The tutorial comes with a script for removing items from a shopping cart, but the remove function doesn't work. I have a few questions regarding some additions to the existing functionality. 1. How to prevent duplicate drag and drops? 2. How to remove an item from a dragable list? 3. How to remove an item from a droppable list? Here is the link for the demo and source code http://demo.superdit.com/jquery/dragdrop_cart/    http://superdit.com/2011/04/02/drag-drop-shopping-cart-using-jquery/