Professor Barman says to Gabriella, I will sell you my car for $$10,000.$ The offer is made while Professor Barman is unlocking and entering a $2020$ BMW$.$ Gabriella says, I accept, and promptly gives Professor Barman $$20$ towards the deal. Professor Barman instructs her to come to his house at $5pm$ with payment. When she arrives, Professor Barman hands her the keys to a $1993$ Ford Escort that he also owns. A likely outcome under the common law:

Contract is not valid due to lack of formation

contract is not valid because the $1993$ Ford is clearly not worth $$10,000$

contract is valid under the mirror image rule.

contract is valid because legal consideration was provided