conversations.from: human
conversations.value: John used to buy 4 coffees a day for $2 each.  They raised the price by 50% so he cut the number of coffees he drinks in half.  How much money does he save per day compared to what he used to spend?
conversations.from: assistant
conversations.value: He now buys 4/2=2 coffees
  The new price is 2*.5=$1 more than the old price
  So he now pays 2+1=$3 per coffee
  So he spends 3*2=$6
  He used to spend 4*2=$8
  So he saves 8-6=$2 per day