Metro Auto Parts Supplies Many Garages with Auto Parts

Metro Auto Parts supplies many garages with auto parts. On its invoice it says that the amount is due in 30 days but will be reduced by 10% if paid within 15 days. Is Metro Auto Parts bound in contract to give its customers the discount if they pay early?

A) No, when a creditor agrees to accept a lesser sum than the full amount of the debt on the due date, there is no consideration for the creditor's promise to waive payment of the debt owed.
B) Yes, when a creditor agrees to accept a lesser sum than the full amount of the debt prior to the due date, there is consideration for the creditor's promise to waive payment of the debt owed.
C) Yes, promissory estoppel would apply.
D) Yes, promissory estoppel does not apply.
E) No, the invoice would have to be under seal.