事情是这样的，我们买房子给了offer过后，卖家counter offer，然后我们又counter
back，要求卖家在某一个时间之前回信。结果卖家拖到第二天才回复
Offer 是这样写的：
This Counter-Offer is binding upon Seller and Buyer only if a copy of the
accepted Counter-Offer is delivered to the Party making the Counter-Offer on
or before 某个时间 (Time is of the Essence). Delivery of the accepted
Counter-Offer may be made in any manner specified in the Offer to Purchase,
unless otherwise provided in this Counter-Offer
这个Offer还有效么？
卖家接受offer后，我们做inspection，发现很多问题，Radon不过关，地下室和attic
都有霉，我们想撤销offer。似乎我们的contract只有给seller修的权利或者Seller
cancel的权利。现在我们想利用这个offer无效来逃脱。
