On April 14, 2007, Seeley Corp. entered into a written agreement to sell to Boone Corp. 1,200 cartons of certain goods at $.40 per carton, delivery within thirty days. The agreement contained no other terms. On April 15, 2007, Boone and Seeley orally agreed to modify their April 14 agreement so that the new quantity specified was 1,500 cartons, same price and delivery terms. What is the status of this modification?

1. Enforceable.
2. Unenforceable under the statute of frauds.
3. Unenforceable for lack of consideration.
4. Unenforceable because the change is substantial.