According to rule of contract formation, which of the following is a valid acceptance?

Once a valid acceptance takes place, a binding contract is formed. It is therefore important to know what constitutes a valid acceptance in order to establish if the parties are bound by the agreement. There are three main rules relating to acceptance:

1. The acceptance must be communicated to the offeree.

2. The terms of the acceptance must exactly match the terms of the offer.

3. The agreement must be certain.

Among the answers:

"The person says that she will think about it overnight" does not match the terms of the offer. The offeree does not assure that she will accept the offer.

"The person asks for a lower price": This is a counter-offer.

"The person states that she is able to pay the offered price" is not certain. The offeree merely provides information on her financial ability.