Dirt simple shipping matrix

shipping_matrix.rb

class ShippingMatrix

  @matrix = {
    (1..10) => 2.50,
    (11..20) => 5.00,
    (21..30) => 10
  }
  
  def self.price_for(quantity)
    @matrix.find { |range, price| range.include?(quantity) }[1]
  end

end

usage.rb

ShippingMatrix.price_for(15)
=> 5.0