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?

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

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.

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

Stan must return the defective gloves to Isaac, who must replace them. Then, Stan must pay the $$800.$