module Speakable
	def speak
		puts "Yo!"
	end
end

class Student
	include Speakable

	attr_accessor :name, :gender, :age

	def initialize(name, gender, age)
		@name=name
		@gender=gender
		@age=age
	end

	def speak
		puts "Yo, my name is #{@name}!"
	end

	def to_s
		return "#{@name} #{@gender} #{@age}"
	end
end

class Senior < Student
	attr_accessor :credits_left

	def initialize(name, gender, age, credits_left)
		super(name, gender, age)

		@credits_left=credits_left
	end

	def to_s
		return super+" Credits left: #{@credits_left}"
	end
end

s1=Student.new("Bob", :m, 14)

puts s1

s2=Senior.new("Betty", :f, 18, 6)

puts s2

puts s1.name

puts s2.credits_left

s1.name="Roberto"

puts s1.name

s1.speak

s2.speak