Final answer:
Mark may not have to pay the promissory notes if he is deemed mentally incompetent as mental incompetence is considered a real defense in contract law, potentially voiding his legal obligation to pay even to holders in due course.
Step-by-step explanation:
The question asks whether Mark, who is mentally incompetent and delights in signing documents, must pay the promissory notes he signed which were negotiated by Henry and held by holders in due course. When considering contracts and negotiable instruments such as promissory notes, a key aspect is the mental capacity of the signer. If Mark is indeed mentally incompetent, he may have a real defense against the enforcement of the notes. In contract law, mental incompetence is a recognized real defense that can void the legal obligation of the contracts, meaning that the promissory notes could be declared void and Mark may not be legally obligated to pay.
Moreover, holders in due course generally have a stronger position, as they can enforce the note free from many defenses that could be raised against the original payee. However, real defenses, such as fraud in the factum, duress, incapacity, or illegality, are exceptions and can in fact be raised against holders in due course. Since the question outlines that Mark has a mental incapacity, this suggests that any contracts or promissory notes he signs could be void or voidable, thus potentially excluding him from the obligation to pay even to a holder in due course. It is important to establish the specifics of Mark's mental incompetence through a legal process to confirm that it would constitute a sufficient defense. If such a defense is accepted, the answer would align with option B: Mark does not have to pay these notes since he has a real defense.