Coin$-$operated car wash 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.

Draw a representative E$-$R diagram for the system, including:

$$ Entities

$$ Sample attributes including candidate key$($s$)$

$$ Relationships

$$ Cardinalities