Identify the following rules as either representative of the common law of contracts or UCC rule on formation of sales and lease contracts. Your answer should be either "Common Law" or "UCC."

$1.$ If the parties to a sales contract do not agree on payment terms, payment is due at the time and place when the buyer is to receive the goods.

$2.$ If the buyer and seller do not agree on or specifically state a price for the services, the contract may fail for a lack of "definiteness."

$3.$ An offer to make a contract may be revoked at anytime unless the offeree has given consideration for the offer to remain open. An option contract.$)$

$4.$ If a contract is required to be in writing under the Statute of Frauds, the writing must be signed by the party aginst whom enforcement is sought.

$5.$ Consideration is not required for modification of a contract.

$6.$ Additional terms of an acceptance can become part of a contract if they do not materially alter the terms of the offer and the offeror does not object within a reasonable time.

$7.$ Offers by merchants to keep an offer open are binding up to three months without any consideration.

$8.$ The "mirror image rule" applies to an offer and acceptance for contract creation.