This short video goes over a small proportion of a course on Inventory Theory that I teach (http://goo.gl/aL8Bk): the Economic Order Quantity Model. This model is arguably the 'simplest' model in Inventory Theory.
In this video I also make use of a Sage code snippet which is here: http://goo.gl/ILg4Q. If you're not familiar with Sage I really recommend you checking it out.