Marvin Mower (MM) is a college student trying to earn a few extra bucks. Marvin mows yards on the side, and he cuts the lawn for Ursula Unhappy (UU). UU writes MM a document for his work. The document acknowledges MM performed work, and that UU owed MM \$50. MM doesn't have time to get to the bank, so MM gives the document to Tommy Thirdparty (TT), who pays him $40 for it. Predictably, before TT can try to recover $50, UU is unhappy with MM's work, and refuses to pay