Looking for a rule statement for the following fact pattern:

k Bonnet is walking through the woods one day and is stung by a bee. She can't get the stinger out and cries for help. Big Bad Bear hears her cry and walks over to Pink Bonnet, sees the stinger in her foot, and pulls it out. Pink Bonnet tells Bear, "Oh, thank you, Mr. Bear. I'm so grateful that I'll send you a large basket of Grandma's homemade blueberry muffins next week. Big Bad Bear is thrilled, and responds, "Wonderful. I will look forward to receiving them." Several weeks pass but no basket arrives. Next time Pink Bonnet walks through the woods, Big Bad Bear stops her and reminds her that she owes him the muffins. "We have a contract," he tells her.