Construct a Entity-Relationship Model (ERM) for the following..

AVS (Arkansas Vehicle Services) sells recreational vehicles. The new system manages vehicle information. Included in the vehicle information is a serial number, model, year, manufacturer and status (e.g., sold or in-inventory). When a customer arrives at AVS, he or she works with AVS staff to buy a vehicle (e.g., negotiating the price). Customer information such as CustomerID, first name, last name and phone number is stored. A staff member serves one or more customers. Each customer is served by one staff member.

The system also manages the staff information including StaffID, FName, LName, Address, Phone, and HireDate. AVS operates more than one service locations. The service location information such as ServiceLocID, Name, Location and Phone is stored. A staff member is assigned to one or more service centers. Each service center is assigned more than one staff member. The assignment dates and the number of hours assigned are required to be recorded so that AVS knows which staff is assigned to which service center, when and for how-long.

Each service center is managed by a manager. A manager manages one service center.

When they agree to buy a vehicle, a sales invoice is created. The database system generates an invoice. An invoice is generated for one customer. Each customer is given an invoice. A vehicle is also involved in an invoice. Each invoice involves one or more vehicles. The invoice includes the information such as InvoiceNo and transaction date. The invoice also includes the final negotiated price, applicable tax and license fee.

If necessary, make explicit assumptions for the relationships.