conversations.from: human
conversations.value: Explain how to solve this math problem: Mark spent 220 dollars to fix his car.  It needed two parts that cost 20 dollars each, and labor cost .5 dollars a minute. How many hours did the mechanic work?
conversations.from: assistant
conversations.value: Labor cost is .5*60=30 dollars per hour
  The cost for parts is 20*2=$40
  The total cost for labor is 220-40=$180
  He spent 180/30=6 hours on labor.