Draw DFDs for the system, including:

$$ Context diagram

$$ Level$-0$ diagram

$$ Representative Level$-$n diagrams for Coin$-$operated car wash which

is a self$-$service car wash system. A customer inserts the required number of quarters to buy a preset period of

wash time. The customer can turn a dial to select soap, foam, rinse, and wax any time during the wash period. The system beeps when

one minute is remaining. The customer can insert more quarters to buy more wash time.