<prompt> Translate the following text to EnglishPia zinalinda subclasses preferred ya barua, viwango vya chini kwa ajili ya magazeti, uainishaji kwamba si soko msingi, viwango kwamba si kufuata gharama, na mbalimbali ya mazoea mengine kujadiliwa katika karatasi hii.  <response>: They also protect the preferred subclasses of mail, low rates for Periodicals, classifications that are not market based, rates that do not follow costs, and a range of other practices discussed in this paper. 