Use the following Fact Pattern to answer the question.

1. In February, Retailer contacted Designer, and asked Designer to design Retailer's website for $20,000, and Designer agreed.
2. Under the terms of the written contract, Retailer was to pay Designer $20,000 by December 31^st for designing the Retailer's website.
3. In August, four months before the payment was due in December, Designer learned of an investment opportunity.
4. Designer called Retailer and said, "I need cash quickly to make an investment that will enable me to make a $35,000 profit.
5. I know that you owe me $20,000 in December, but if you promise now to pay me $15,000 in cash by the 25th of this month (August), I will accept that as the full payment for designing your website."
6. Retailer responded, "Thanks. That's a good deal. I accept, but only if I can get a loan, as I do not have the cash right now."
7. "Thanks, that would be great," responded Designer.

QUESTION: Would the agreement in lines 1-2 be covered by the Common Law or the UCC? How do you know?