conversations.from: human
conversations.value: Jack bought 3 books a month at $20 each.  He sells them back at the end of the year for $500.  How much money did he lose?
conversations.from: assistant
conversations.value: He bought 3*20=$60 of books a month
  That means he bought 60*12=$720 of books a year
  So he lost 720-500=$220