Give me your opinion

[Bryan .]

I was negotiating on a REO property owned by a bank. After many delays I finally gave them a "final and best offer" of $117,300 in which I required an answer by the end of the day (last Tuesday). They came back to me and accepted my offer if I agreed to close by Nov 16 and completed my inspections within 5 days. I agreed and signed the offer. I assumed I had a deal. I was notified of Friday that the "supervisor" did not agree with the price and now needed $121,000 or the deal would not go through. I think the law in Pennsylvania states that if a party makes a counter offer and the other party accepts, you have a contract. I advised my agent that I would not pay more than the $117,300. I am considering getting an attorney involved, but I don't want to end up spending more time and money than it's worth. Any opinions?