when can an offer to form a unilateral contract be revoked
Offer and acceptance An offeror may revoke an offer before it has been accepted, but the revocation must be communicated to the offeree (although not necessarily by the offeror,[16]). If the offer was made to the entire world, such as in Carlill's case,[5] the revocation must take a form that is similar to the offer. However, an offer may not be revoked if it has been encapsulated in an option (see also option contract), or if it is a "firm offer" in which case it is irrevocable for the period specified by the offeror.
Listing contract In the event of multiple offers being presented, the seller may accept whichever offer is most suitable to him/her, even if the price is not the highest. The percentage commission will be paid according to the accepted price. The seller, often in concurrence with the real estate agent, may choose to accept an offer that is lower than the highest offer for various reasons, such as terms or contingencies in the purchase contract offered or perceived differences in financial qualification of the competing buyers.