conversations.from: human
conversations.value: John has to replace the ball bearings for machines he works with.  He has 10 machines and they take 30 ball bearings each.  It normally costs $1 per ball bearing but right now there is a sale where they are only $.75.  Also since he is buying in bulk he gets a further 20% discount.  How much money did he save by buying them all during the sale rather than 1 at a time?
  Solve it.
conversations.from: assistant
conversations.value: He needs to replace 30*10=300 ball bearings
  The normal price is 300*1=$300
  Because of the sale he only has to pay 300*.75=$225
  He then gets a discount which shaves another 225*.2=$45 off the price
  That means he only pays 225-45=$180
  So he saved 300-180=$120