$($b$)$ Consider a software system which will be embedded in ticketing machines

used to issue train tickets. Travellers wishing to buy a ticket can buy a oneway ticket, a weekly commuter ticket, or a monthly commuter ticket. A ticket

can be paid for by cash or credit card and card is most typical. If a person

does not enter the full cash required or a card within $30$ seconds of starting

to purchase a ticket, the machine automatically times out the transaction. If a

person wishes to cancel a transaction, they simply press the cancel button.

Changes in ticket fares are communicated to all ticket machines from the

train company$$s management system. If the machine is out of paper, no

tickets can be issued and so no transactions should be allowed to start. If the

machine is out of change, no cash transactions should be allowed to

complete unless exact fare is given.

$($i$)$ Write the detailed form of the main scenario of the $$Buy Ticket$$ use

case.

$($ii$)$ Identify four extension scenarios for the use case in part $($i$)$ and

document each one in the brief style $($indicating the condition in which

the extension occurs and the basic action that results$)$