Cost Reporting

As a user, I want to get a description of all the costs for a complete account.

1. The user provides an inventory description for a time period. The inventory describes all elements present, including those created and destroyed within the period.
2. The user provides metrics for the elements in the inventory
3. The user provides a price plan, that includes all rates applicable.
4. The user call rating with the inventory, metrics and the price plan.
5. The result is a list back with the charges associated to the inventory, including discounts.