Here are some requirements for an ATM system. Classify each one as either functional or non$-$functional requirements. Note: If a requirement contains a functional and a nonfunctional aspect, classify it as non$-$functional requirement.

The ATM unit consists of a display, a card reader, a cash dispenser, an envelope drawer, an envelope slot, a keypad and a printer.

The card reader determines the account number from the entered card. The ATM is in the idle state when there is no operation.

The keypad is a set of buttons that includes the following: $10$ buttons labeled with numbers $0$ to $9,$ an OKAY button, a CLEAR button, a CANCEL button, and dynamic buttons that perform different actions.

The User is prompted to enter a PIN after a card is entered.

A PIN must be entered within $20$ seconds.

A menu is displayed to the User with the following options: Withdraw, Deposit, Pay Bill, Account Update, and Exit.

The User must enter the PIN correctly within three attempts The printer can be opened and refilled with paper.

The cash dispenser has the ability to dispense cash.

The ATM can be shut down and restarted remotely

A transaction record can be printed upon demand.

The card is ejected when the session is completed.

The envelope feeder accepts envelopes from the customer

$\_$ The cash dispenser can be opened and refilled with cash.