Mark sold his car to Mary.Mary paid with a certified check.The check was made out for $18,000,the agreed-upon price for the car.After they had exchanged paperwork and closed the deal on the car,Mark noticed that the bank had certified the check for $10,000,rather than the $18,000 amount of the check.Mark then altered the check to be for $28,000.How much must the bank pay on the check?