The following depicts a main path through the use case, 'Return Item':
USE CASE: Return Item
Use case ID: UC14
Purpose: Customer selects an item for return and prints return label
Actors: Customer, System
Pre-conditions: Customer has opened shopping site home page

The following Exceptions have been defined:
E1. Customer is already logged-in to account, therefore Main Menu displayed. Occurs at step M2.
E2. Invalid Log-in details entered, prompt for re-try. Occurs at step M4.
E3. Third invalid log-in attempt, account frozen for 24 hours and process ended. Occurs at step M4.
E4. Go-Back requested. Occurs at steps M7 (to go back to 'Main Menu') and M9 (to go back to
'Order History' screen).
You are to apply the Use Case test technique, where the following coverage rules have been defined in the test plan:
One test case should be designed for the basic behaviour.
Multiple alternate behaviours may be incorporated into a single test case provided they are mutually compatible.
Nested alternate behaviours, where there are termination versus non-termination alternate behaviours within a "retry" exception behaviour, should be amalgamated into single test case.
Applying these rules to the Return Item Use Case, how many test cases should be designed?