new_contents: # cars number
  cars = 100
  # a car have 4 space
  space_in_a_car = 4.0
  # drivers number
  drivers = 30
  # passengers number
  passengers = 90
  # the number which car haven't driver
  cars_not_driven = cars - drivers
  # the number which car have driver
  cars_driven = drivers
  # the number that total cars can pass people
  carpool_capacity = cars_driven * space_in_a_car
  # the average of passengers in each car.
  average_passengers_per_car = passengers / cars_driven
  
  print "There are", cars, "cars available."
  print "There are only", drivers, "drivers available."
  print "There will be", cars_not_driven, "empty cars today."
  print "we can transport", carpool_capacity, "people today."
  print "we have", passengers, "to carpool today."
  print "we need to put about", average_passengers_per_car, "in each car."
  
subject: add var.py