Alan Fulkins, who owns a construction company that specializes in single-family residences, is constructing a small subdivision with 23 homes. Tretorn Plumbing, owned by Jason Tretorn, was awarded the contract for the plumbing work on the homes at a price of $4,300 per home.

Plumbing contractors complete their residential projects in three phases. Phase one consists of digging the lines for the plumbing and installing the pipes that are placed in the foundation of the house. Phase two consists of installing the pipes within the walls of the home, and phase three is installing of the surface plumbing, such as sinks and tubs. However, industry practice dictates that the plumbing contractor receive onehalf of the contract amount after completion of phase one.

Tretorn completed the digs of phase one for Fulkins and received payment of $2,150. Tretorn then went to Fulkins and demanded an additional $600 per house to complete the work. Fulkins said, "But you already have a contract for $4,300!" Tretorn responded, "I know, but the costs are killing me. I need the additional $600."

Fulkins explained the hardship of the demand, "Look, I've already paid you half. If I hire someone else, I'll have to pay them two-thirds for the work not done. It'll cost me $5,000 per house."

Tretorn responded, "Exactly. I'm a bargain because the additional $600 I want only puts you at $4,900. If you don't pay it, I'll just lien the houses and then you'll be stuck without a way to close the sales. I've got the contract all drawn up. Just sign it and everything goes smoothly."

Should Fulkins sign the agreement? Does Tretorn have the right to the additional $600? Was it ethical for Tretorn to demand the $600? Is there any legal advice you can offer Fulkins?