Luke is baby-sitting for Gloria. She expects him to care for her son in a responsible way. When Luke posts a selfie on social media, Gloria worries that her son might be in danger. This represents the principal-agent problem. Luke is the agent and Gloria is the principal. Is he acting in her best interest? Of course not! He’s shirking. To cover up his shirking, Luke tells Gloria that he has a series of photographs of her son in dangerous situation but they’re all fake. Now, he needs a series of photoshopped pictures but doesn’t use photoshop. So, he decides to only give Manny something that he wants if he photoshops Gloria’s younger son in to dangerous situations. This represents trade through barter. Luke has a pass that Manny wants. Manny has a skill that Luke needs. They trade because they have a double coincidence of wants.