Create an ER Diagram for the following description:

[The ERD should show all entities, relationships between entities and cardinality including mandatory-optional requirements.]

XYZ is an online retailer that sells apparel and accessories. The company offers fashionable and affordable clothing, shoes and accessories.

XYZ has enjoyed steady sales and earnings growth and has a need to automate their reporting system. The company needs a database that will record sales, gather customer information, and provide stock information.

The system will store information for each customer like name, address, phone number, and email. The system will use unique IDs assigned to each customer for recording transactions. The system will use unique IDs for each inventory item. Customers will also be able to track their orders with a unique tracking number.