conversations.from: human
conversations.value: Mark needs to replace the radiator in his car.  The work takes 2 hours and the mechanic charges $75 an hour.  The part cost $150.  How much did he pay?
conversations.from: assistant
conversations.value: He had to pay for 2 hours of labor, which cost 2*$75=$150
  So the total cost was $150+$150=$300