<prompt> Translate the following text to EnglishKama ilivyoelezwa hapo awali, faida kutoka barua iliyotolewa na isiyowasilishwa lazima iwe sawa na gharama ya juu ya mtiririko katika chapisho la kuvunja.  <response>: As stated earlier, the profits from delivered and non-delivered mail must equal the upstream fixed cost in a breakeven post. 