<prompt> Translate the following text to EnglishMfano ni kutumika kutambua mwenendo katika gharama marginal na retrofits, ukubwa takriban wa mwenendo huo, na sababu za mwenendo huo.  <response>: The model is used to discern trends in marginal costs and retrofits, the approximate magnitudes of those trends, and the reasons for those trends. 