conversations.from: human
conversations.value: James paints a 20 ft by 15 ft mural.  It takes him 20 minutes to paint 1 square foot and he charges $150 per hour.  How much does he charge to paint the mural?
  Find the solution.
conversations.from: assistant
conversations.value: The mural is 20*15=300 square feet
  So it takes him 300*20=6000 minutes
  So he paints it in 6000/60=100 hours
  That means he charges 100*150=$15000