specific_calculators.rb

class BankA  
  module Result3
    def self.call(result_1:, result_2:, **kwargs)
      result_1 - result_2
    end
  end
  
  def evaluation_steps
    {
      result_1: ::Defaults::Result1,
      result_2: ::Defaults::Result2,
      result_3: ::BankA::Result3,
    }
  end
end

class BankB
  module Result3
    def self.call(result_1:, result_2:, **kwargs)
      if result_2 > 0
        (result_1 - result_2)
      else
        result_1
      end
    end
  end
  
  def evaluation_steps
    {
      result_1: ::Defaults::Result1,
      result_2: ::Defaults::Result2,
      result_3: ::BankB::Result3,
    }
  end
end