<prompt> Translate the following text to EnglishKwa kuwa gharama hizi ni kutofautiana kwa muda mrefu na hatujui jinsi utawala mwingine wa posta kushughulika nao, sisi parameterize yao kwa madhumuni ya modeling.  <response>: Since these costs are variable in the long run and we do not know how other postal administrations deal with them, we parameterize them for purposes of modeling. 