building.rb

class Building
	attr_reader :address

	def initialize(rooms, address, width, length)
		@rooms = rooms
		@address = address
		@width = width
		@length = length
	end
	
	def area
		@width * @length
	end

	def Building.price_per_square_meter(city)
		case city
		when "São Paulo" then 8000
		when "São Cateano" then 5000
		else puts "Não conheço essa cidade"
		end
	end
end

butler.rb

class Butler
	attr_reader :castle

	def initialize(name, castle)
		@name = name
		@castle = castle
	end

	def salary
		10 * castle.area
	end
end

castle.rb

require_relative "building"
require_relative "butler"
require 'pry'

class Castle < Building
	attr_reader :butler

	def initialize(rooms, address, width, length, butler = nil)
		@butler = Butler.new(butler, self) if butler
		super(rooms, address, width, length)
	end

	def has_a_butler?
		@butler != nil
	end

	def area
		super + 300 # + jardim
	end

    def self.categories
    	['Medieval', 'Norman', 'Ancient', 'Fantasy']
    end
end

house.rb

require_relative "building"

class House < Building
end

inheritance.rb

require_relative "house"
require_relative "castle"

ebac = House.new(50, "Mourato Coelho 1404", 14, 36)

itaipava = Castle.new(200, "Castelo de Itaipava", 100, 100, "Jenkins")
itaipava.area
p itaipava

if itaipava.has_a_butler?
	puts "Itaipava tem um mordomo!"
else
	puts "Itaipava não tem um mordomo..."
end

greyskull = Castle.new(500, "Castelo de Greyskull", 500, 500)
if greyskull.has_a_butler?
	puts "Greyskull tem um mordomo!"
else
	puts "Greyskull não tem um mordomo..."
end

[itaipava, greyskull].each do |building|
	puts "#{building.address} - #{building.area}m²"
end

puts Castle.categories
puts greyskull.class.categories