# mixin_2.rb

module Constants
  Pi = 22.0/7
end

class Circle
  include Constants
  attr_accessor :radius

  def area
    Pi * radius * radius
  end
end

class Sphere
  include Constants
  attr_accessor :radius

  def volume
    (4.0/3) * Pi * radius ** 3
  end
end

c = Circle.new
c.radius = 7
s = Sphere.new
s.radius = 7
puts "Circle Area = #{c.area}"
puts "Sphere Volume = #{s.volume}"