Helen collects rare jewellery. Her favourite piece of jewellery is a rare necklace which she bought overseas and wears on special occasions. While having dinner with her family one night, Helen's sister, Lucy, asks her if she can buy the necklace.

Helen says, "I'm not against you buying the necklace. I would sell you the necklace for $1,250. How does that sound?"

Lucy replies, "$1,250 is a little too much money. I can't afford that. How about $1,000?"

Helen says, "Sure, that's okay. I can do that. That's a deal."

Helen gives Lucy the necklace and in exchange, Lucy gives Helen $1,000 in cash.

The following week at dinner, Lucy asks Helen: "Is the necklace I bought from you last week made of 100% gold?"

Helen says: "Yes, it is."

Unfortunately, Lucy discovers that the necklace is made of only 50% gold. Lucy is now upset and wants Helen to repay the $1,000.

Advise Helen if a valid legal contract has been formed with Lucy and whether Helen's promise that the necklace is made of 100% gold can be enforced. Do not discuss any material outside of Contract 1.