Discover ambiguities or omissions in the following statement of requirements for a ticket issuing system.

• An automated ticket issuing system sells rail tickets.
• The rail ticket is issued and their credit card account charged with its cost.
• When the user presses the start button, a menu display of potential destinations is activated along with the message to the user to select a destination.
• Once a destination has been selected, users are requested to input their credit card.
• When the credit transaction has been validated, the ticket is issued.