4)

A baker sold cookies at a farmer's market in her small coastal town every week. One week she experimented with a new type of cookie that she called a "penguin" which was a chocolate and vanilla cookie with frosting made to look like icicles. That week, a wealthy tourist passing through the town stopped at the farmer's market and bought a penguin cookie. The tourist loved the cookie, and said she wanted to buy as many as possible to send back to her friends and family. The tourist agreed she would stop back at the farmer's market and buy "as many penguins" as the baker could make in the next week for $2 apiece. The baker agreed, and went to work baking 1,000 penguin cookies over the next week. At the next week's farmer's market, the tourist failed to show up. The baker tracked the tourist down, but the tourist said she was back on her diet and did not want to be tempted by all the cookies, so she was no longer interested in the penguin cookies. The baker sued the tourist for $2,000.

What is the tourist's best argument that there was not a valid contract?