<prompt> Translate the following text to SwahiliFurthermore, high postal densities reduce the impact of volume on unit street delivery costs, and high volume reduces the impact of postal density.  <response>: Kwa kuongezea, wiani wa posta wa juu hupunguza athari za kiasi kwenye gharama za kitengo cha utoaji wa mitaani, na kiasi cha juu hupunguza athari za wiani wa posta. 