Caterer Agrees with Bride to Cater Bride's Wedding Reception for $12

Caterer agrees with Bride to cater Bride's wedding reception for $12 per plate.On the wedding day,Caterer calls Bride saying that some things have come up,and she will have to charge $16 a plate in order to do the catering.Bride agrees.Which is true?

A) The $16 is not enforceable because the $12 per plate was past consideration.
B) The $16 is not enforceable because of a preexisting duty.
C) The $16 is enforceable if the reason for it was beyond Caterer's control.
D) The $16 is not enforceable because it means the $12 was an illusory promise.
E) The $16 is enforceable if Bride could have found another caterer before the wedding.