2.1 If customer does not exist,then the clerk pauses this use case and invokes Maintain customer information use case.
2.2 If customer has a credit hold,then clerk transfers the customer to a customer service representative.
4.1 If an item is not in stock,then customer can
a. choose not to purchase item,or
b. request item be added as a back-ordered item.
9.1 If customer payment is rejected due to bad-credit verification,then
a. order is canceled, or
b. order is put on hold until check is received.