Russ Wrote a Check to Buy Some Motors from Sam's

Russ wrote a check to buy some motors from Sam's Small Engine Shop.Before the check was cashed,Russ stopped payment on it because he found out the motors were not powerful enough for his needs and he was going to return them.The bank negligently paid the check over the stop payment order.Discuss what makes a stop payment order valid,including the length of time for which a stop payment order is effective,and whether a bank has liability for paying a check over a stop payment order.