The following data elements comprise the conceptual-level schema for a database:

billing address cost credit limit customer name customer number date description invoice number item number price quantity on hand quantity sold shipping address terms Required

a. Identity three potential users and design a subschema for each. Justify your design by explaining why each user needs access to that data element.

b. Using any relational database product, such as Microsoft Access, create the set of tables to implement your schema. Specify the primary key(s) and foreign key(s) for each table. Learn how to enforce referential integrity, and test your model by entering sample data in each table.