Stan purchased 400 pairs of gloves from Isaac at a contract price of $800. Fifty of the gloves were defective, and a dispute arose as to the amount due and owing under the contract. Stan refuses to pay the $800, and Isaac is threatening to sue. Which of the following is correct with regard to this transaction?

a.If Isaac agrees to accept $600 to settle the dispute and Stan agrees to pay that amount, the substitute agreement is enforceable.

b.If Isaac agrees to accept $600 to settle the dispute and Stan pays that amount, Isaac can still sue for the balance of $200 and will win the lawsuit.

c.Stan is under a pre-existing legal obligation to pay the $800.

d.Both (b) and (c).