<prompt> Translate the following text to EnglishVipimo vya kutolewa kwa kila kiwanda cha umeme ni msingi wa uzalishaji wa 1997 kwa kutumia formula ambayo haidhuru viwanda safi ambavyo tayari vina kiwango cha chini cha uzalishaji wa NOx au SO2.  <response>: Allowances are allocated to each power plant based on 1997 emissions using a formula that does not penalize the clean plants that already have a low NOx or SO2 emission rate. 