A local bookstore invites you to design a database system for them based on the following requirements.

Basic Requirements

1. Books information includes book name, authors, book type, price, and units in inventory.

2. One book will only have one book type. One book type can contain many books.

3. The store has different areas to organize different types of books. One book type can only be located in one area. One area can contain many book types.

4. A membership system, with customers information including name, phone number, balance, ...

5. Customers can search books by an author's name. However, one book may have multiple authors.

6. An invoice system, a customer can buy more than one books at one time.

Please design a database for this bookstore. Draw the ERD. (You may need to add necessary attributes.)