Entity-Relationship model for car rental bus.

I am working on an Entity-Relationship mode for car rental business.

The problem I am facing is how to connect vehicle entity with the contract entity and if there is any additonal entities needed to do the following.

-In one contract, you could have many vehicles, e.g., v1, v2, v3 and v1 again. Example: Renter can rent a car and then change it for some reason. Also, renter can rent more than one car. Finally, renter can rent more than one car.

Thank you for your help. :)