Can the contract be enforced? see below story.?

Jon settled on a price with a dealer for a new car, with final agreement contingent on an acceptable amount for the trade-in. But the seller noted in the agreement that trade-in car is 2008 BMW instead of 2007. Jon noticed that difference but did not say anything and signed the contract. A few minutes later the salesman came back and said the deal is off because he had based the trade-in allowance based on BMW 2008. Jon said he would take the deal as is and not a lower trade-in allowance. After some negotiations dealer agreed to sign the contract with originally stated trade-in allowance. Jon signed the contract and left. Next morning the dealer notified Jon that the contract is rescinded due to the mistake. Can Jon enforce the contract? Why?