dialogue: Sanson: May I have my bill, please? 
  Millicent: That's $20 in all. 
  Sanson: Well, I am afraid you have made a mistake. Would you check it again, please? 
  Millicent: Let me see. I am terribty sorry, sir. That should be $18. 
  Sanson: It doesn't matter. 
summary: Sanson points out a mistake on Sanson's bill.