A mailing is to be sent out to customers. The content of the mailing is about the current level of discounting and potential levels of discounting. The content is different for different types of customers.

Customer Types A$,$ B$,$ and C get a normal letter except Customer Type C$,$ who gets a special letter. Any customer with $2$ or more current lines or with a credit rating of $\text{'}$X$\text{'}$ gets a special paragraph added with an offer to subscribe to another level of discounting.