Sami walks into a restaurant. She is given a menu, which indicates that lobster is $30. Sami orders the lobster. It arrives, and Sami thinks it is very tasty. When the bill arrives, Sami tries to execute a clever ploy she learned about in her business law class. She writes a check to the restaurant for $20, and writes "full settlement" across the top. The waiter accepts the check without looking at it, and the restaurant manager later deposits it in the restaurant's bank account. Is this a liquidated or an unliquidated debt? Is Sami off the hook for the last $10?