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A description of the behavior of an Automated Bank Machine (ABM) is given below. Draw a state machine diagram describing its behavior. (25 points) A user begins a transaction at the ABM by entering a bank card. If the card is readable by the machine, the user is prompted to enter their personal identification number (PIN). Once this number has been entered, a menu is presented to the user containing the following options:

show account balance,

withdrawal, with receipt and

withdrawal, without receipt. If the user selects one of the withdrawal options, they are prompted to enter an amount of money to withdraw: the amount entered must be a multiple of 10. The users PIN is validated when the ATM sends the details of the transaction to the banks remote computer. The remote computer responds, either approving the transaction or with a message saying that the PIN is invalid. If the PIN is invalid, the user is given the option of re-entering it (provided s/he has not entered three invalid PINs) and the selected transaction is retried. Once three invalid PINs have been entered, the transaction is terminated. If a valid PIN is entered, further processing depends on the transaction type selected. For a show balance transaction, the balance is displayed on the screen. The user has to confirm that s/he has seen it and the user is returned to the transaction menu. A withdrawal transaction may fail if the user has exceeded the amount of money that can be withdrawn from the account; in this case an error message is displayed and, after the user confirms s/he has seen it, the user is returned to the transaction menu. Otherwise, the users card is returned and the money is issued, followed by the receipt if required. Hint: The balance is available from the remote computer. The machine may enter some state where it communicates the PIN and the operation (either to find the balance or attempt to withdraw the amount stipulated by the user). The remote computer may give any one of the following responsesa) the PIN is invalid and the attempt # by the user, b) the operation to withdraw the specified amount of money is valid, c) the account balance. Use the response by the remote machine to make a transition to the appropriate state.