Write the following process in structured english:

iPhone inventory system:

Move iPhones from the inventory to the sale stage for a customer purchasing the item or placing the order in backlog if the phone is not available.

Give 10% discount to "preferred customers" on the initial order

and

an additional 10% for backlog orders.

Give regular customers 10% discount on backlog orders only.

Give new customers a flat 5% discount whether or not the iPhone is on backorder only.