<prompt> Translate the following text to EnglishUtoaji kazi ni chanzo muhimu zaidi ya tofauti za gharama asili kati ya maeneo ya kijiografia kuhudumiwa na post na, kwa kweli kati ya posts wenyewe.  <response>: The delivery function is the most important source of inherent cost differences between the geographic areas served by a post and, indeed between posts themselves. 