Consider the following statement of requirements for part of system for issuing train tickets. List several ambiguities that exist within the statement of requirements that would need to be clarified during the requirements engineering phase. Also, write a set of non-functional requirements for the ticket-issuing system described above, especially focusing on its expected reliability and response time.

Scenario:

An automated ticket machine sell rail tickets. Users select their destination and input a credit card and a personal identification number. The rail ticket is issued and their credit card account is charged. When the user presses the start button, a menu display of potential destinations is activated, along with a message to the user to select a destination and the type of ticket required.Once a destination has been selected, the ticket price is displayed and customers are asked to input their card. Its validity is checked and the user is then asked to input his other personal identifier (PIN). When the credit transaction has been validated, the ticket is issued.