Guidance in drawing a use case diagram

So basically Ive been asked to create a use case diagram for the following scenario:

Users of the application will be any staff member booking a car from the pool, and staff in the Transport Office who are responsible for maintaining all the data and for allocating the long-term cars.
Maintaining the data involves tasks such as adding new cars, deleting cars that have been sold, and updating cars, e.g. recording service dates (when a car is due for a service and when it was last serviced), changing the status of a car when it is no longer required and waiting to be sold, making a car unavailable if it is damaged and awaiting repair.
Cars booked from the pool are booked for whole days, so, for example, if a member of staff needed a car, he/she would access the system on the day it was required and select a car from those available. The car would then be allocated to that member of staff for that day only.

Here is a list of actors and use cases ive come up with

Teachers -   Booking cars

Staff   Booking cars
              Adding new cars
              Deleting sold cars
              Updating cars   1. Recording service dates
                                          2. Changing status to when its being sold
                                          3. Making cars unavailable if waiting for repair.

I can see that im going to have to use extend association on the updates car but i cant see anything else. Was wondering if anyone could tell me if they can see any more use cases or dependencies?

Cheers