Final answer:
Mary and John have joint and several liability so either could be liable for the full amount of the dishonored check.
Step-by-step explanation:
Mary and John have joint and several liability, so either could be liable for the full amount of the dishonored check. When two parties are jointly and severally liable, it means that each party is individually responsible for the entire obligation. This means that the creditor can choose to pursue either Mary or John for the full amount owed.