conversations.from: human
conversations.value: Tim decides to start selling necklaces he makes.  He uses 10 charms to make each necklace.  Each charm cost $15.  He sells the necklace for $200.  How much profit does he make if he sells 30?
  How to solve this?
conversations.from: assistant
conversations.value: Each necklace cost 10*15=$150 to make
  So he makes a profit of 200-150=$50 each
  So his total profit is 50*30=$1500