A car rental company has several car rental agencies across the country. The agencies rent several classes of vehicles:compact, midsize, full size, sport utility. Each vehicle is managed by one agency. Customers rent vehicles from the different agencies. When a vehicle is rented, a new rental record is added to the Rental table with dateout as the current date and dateReturned is left null. When a vehicle is returned the record is updated by filling in the DateReturned field. A portion of the car rental table is given below.

Vehicle(VehicleId, VehicleClassId, AgencyId)
Rental( RentalId, VehicleId, CustomerId, DateOut , DateReturned)
Customer( CustomerId, CustomerName, CustomerBalance)
Agency( AgencyId, AgencyLocation)
vehicleClass(VehicleClassId, VehicleClass, RentalRate)


help needed in creating an entity relationship diagram