conversations.from: human
conversations.value: The educational shop is selling notebooks for $1.50 each and a ballpen at $0.5 each.  William bought five notebooks and a ballpen. How much did he spend in all?
  Find the solution.
conversations.from: assistant
conversations.value: The cost of the six notebooks was 5 x $1.50 = $7.5.
  Therefore, William spent a total of $7.50 + $0.50 = $8 in all.