Which of the following examples might NOT satisfy the "sum certain" requirements of UCC Article 3?
A. The sum stated is $500
B. The sum stated is "$500 plus collection costs and attorney's fees"
C. The sum stated is "$500 plus 10% interest after October 1st"
D. The sum stated is "$500 plus interest at 2 points over prime"
E. The sum stated is "$500 plus four hours of consulting time"