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testq.rb

class Cylinder
   def initialize(r,h)
     @r = r
     @h = h
   end
   def volume
     pi * r * r * h
   end
end

class Can < Cylinder
   def initialize(r,h,price,title)
     super(r,h)
     @price = price
     @title = title
   end

   attr_accessor :price
end

cans = []
cans << Can.new 5,5,5,'beer'
cans << Can.new 5,5,5,'soda'
cans << Can.new 5,5,5,'water'

cans.max_by { |can| can.volume/can.price }