Retired schoolteacher walking down village street. A Rolls Royce approaches, driver (a former pupil) sees teacher, stops, climbs out, effusive greetings. They reminisce for 30 minutes, then teacher says "Smith, you were the laziest in the class and refused to learn. Now you can afford a Rolls Royce". Pupil replies "Yes, Sir, I sell cardboard boxes". Teacher: "Whaat ? You make money out of cardboard boxes ?". "Yes, sir, I buy them for $1 and sell them for $3 and live off the 2% difference".