Final answer:
There is no contract because Seller B's counteroffer served as a rejection of Buyer A's original offer, and Buyer A did not respond. Seller B can indeed change his mind and can make a new offer, which Buyer A would need to accept for a contract to be formed.
Step-by-step explanation:
When Buyer A offers $400,000 to purchase Seller B's house, and Seller B counters with $450,000, Buyer A's silence does not constitute rejection or acceptance of the counteroffer. In contract law, a counteroffer generally serves as a rejection of the original offer and proposes a new offer.
When Seller B later decides to accept Buyer A's original offer of $400,000, technically, the original offer was no longer in play after Seller B's counteroffer, and thus, there would need to be agreement on terms and a new acceptance to form a contract.
As such, Option 2 is closest to being correct; there is no contract because the original offer was constructively rejected by Seller B's counteroffer, and Buyer A never responded to it.
However, by indicating later that he will take $400,000, Seller B is essentially making a new offer to Buyer A. This new offer is identical to the original, but it must be accepted by Buyer A for a contract to be formed. Buyer A is not obligated to offer a higher price, and Seller B can change his mind after previously making a counteroffer.