The key elements of the UCD are:

Actors:

Prospective Customer $($PC$)$

Registered Customer $($RC$)$

Restaurant $($R$)$

Delivery Driver $($DD$)$

Use Cases:

Create Account $($UC$1)$

View Menu $($UC$2)$

Place Order $($UC$3)$

Notify Order $($UC$4)$

Assign Delivery $($UC$5)$

Pick Up Order $($UC$6)$

Deliver Order $($UC$7)$

Provide PIN $($UC$8)$

Relationships:

PC initiates the "Create Account" use case.

RC initiates the "View Menu", "Place Order", and "Provide PIN" use cases.

The "Place Order" use case triggers the "Notify Order" use case.

The "Notify Order" use case triggers the "Assign Delivery" use case.

The "Assign Delivery" use case is used by the "Delivery Driver".

The "Pick Up Order" and "Deliver Order" use cases are performed by the "Delivery Driver".

This UCD provides a clear visual representation of the key functionality and interactions within the Over Eat food delivery service, as described in the case facts.