1. Create the initial ER diagram for a car dealership. The dealership sells both new and used cars, and it operates a service facility. Base your design on the following business rules:
   1. A salesperson can sell many cars, but each car is sold by only one salesperson.
   2. A customer can buy many cars, but each car is sold to only one customer.
   3. A salesperson writes a single invoice for each car sold.
   4. A customer gets an invoice for each car(s) he buys.
   5. A customer might come in only to have a car serviced; that is, one need not buy a car to be classified as a customer.
   6. When a customer takes in one or more cars for repair or service, one service ticket is written for each car.
   7. The car dealership maintains a service history for each car serviced. The service records are referenced by the cars serial number.
   8. A car brought in for service can be worked on by many mechanics, and each mechanic can work on many cars.
   9. A car that is serviced may or may not need parts. (For example, parts are not necessary to adjust a carburetor or to clean a fuel injector nozzle.)