A guy is walking down the street when he sees a sign in a shop window: "We solve any problem! Guaranteed or $100 back."
Intrigued, he walks in and sees a man sitting behind a desk. "Any problem?" the guy asks.
"Any problem," the man says.
The guy decides to test him. "Okay, I’ve lost my sense of taste. I can’t taste anything. Solve that."
The man nods, turns to his assistant, and says, "Bring me Box 22." He opens the box, takes out a small spoonful of a green substance, and tells the guy to eat it.
The guy swallows it and immediately starts coughing and gagging. "Ugh! That’s gasoline!"
The man smiles. "Congratulations, your sense of taste has returned. That’ll be $50."
The guy is annoyed that he got tricked, so he comes back a week later, determined to get his $100. "My memory is gone," he says. "I can’t remember a single thing."
The man nods and says to his assistant, "Bring me Box 22."
The guy shouts, "Wait! That’s the box with the gasoline in it!"
The man smiles. "Congratulations, your memory has returned. That’ll be $50."