Andrew agrees to paint Betty's house for $2,000. Two days after he starts the job, he decides that $2,000 is not enough money. He refuses to finish the job unless Betty agrees to pay him $1,000 more. What law applies to this fact situation

a. The acceptance of additional money to settle a disputed claim is supported by consideration.
b. A past obligation is sufficient consideration for a new promise.
c. Andrew gives no additional consideration in return for modification of a preexisting contract.
d. Betty has made a promise in exchange for a forbearance.