Payment can’t be enforced a minor. But the instrument can be against against A.
Refer Sections 9 and 26 of the Negotiable Instruments Act stated below: 9. Holder in due course. “Holder in due course” means any person who for consideration became the possessor of a promissory note, bill of exchange or cheque if payable to bearer, or the payee or indorsee thereof, if payable to order, before the amount mentioned in it became payable, and without having sufficient cause to believe that any defect existed in the title of the person from whom he derived his title.
26. Capacity to make, etc., promissory notes, etc. Every person capable of contracting, according to the law to which he is subject, may bind himself and be bound by the making, drawing, acceptance, indorsement, delivery and negotiation of a promissory note, bill of exchange or cheque.
Minor.-A minor may draw, indorse, deliver and negotiate such instruments so as to bind all parties except himself. Nothing herein contained shall be deemed to empower a corporation to make, indorse or accept such instruments except in cases in which, under the law for the time being in force, they are so empowered.