The seller has changed the price and closing date originally presented by a buyer and submits this back for the buyer’s acceptance. This is best described as

An amended offer refers to a modification of the original offer's terms without creating a new proposal. In this case, since the seller is changing the price and closing date, it does not simply amend the original terms but rather introduces a new offer that requires acceptance, thus making it a counteroffer instead.

A conditional acceptance implies that the original offer is accepted with stipulations but remains in effect. However, in this scenario, the seller's changes to the price and closing date do not accept the original offer but instead propose a new set of terms, indicating that the original offer is no longer valid.

A counteroffer typically negates the original offer, meaning that both cannot coexist. The seller's changes indicate a new proposal that must be accepted or rejected, which means the original offer is canceled rather than continuing alongside the new terms.