Contract law as to offers is applicable to a sales contract, with the following exception. A firm offer by a merchant cannot be revoked if the offer: (i) expresses an intention that it will not be revoked; (ii) is in a writing; and (iii) is signed by the merchant.
An express period of irrevocability in the offer cannot exceed three months. If nothing is said as to the duration of the offer, the offer can be revoked after a reasonable time. A firm offer is effective regardless of whether the merchant received any consideration to keep the offer open.
An offer to buy or sell goods may be accepted in any manner and by any medium that is reasonable under the circumstances. However, if a specific manner or medium is clearly required by the terms of the offer or the circumstances of the case, the offer can only be accepted in that manner.
Unless it is expressly specified that an offer to buy or sell goods must be accepted just as made, the offeree may accept an offer and at the same time propose an additional term. This form is clear that the offer is not subject to change.