<prompt> Translate the following text to EnglishKama una kifuniko ngumu, kama vile ungefanya chini ya S. 556, kuhitaji kupunguzwa kwa uzalishaji katika chanzo maalum hakupunguzi kiwango cha jumla cha uchafuzi, inazuia tu kubadilika kwa tasnia kuhusu wapi kufanya kupunguzwa.  <response>: When you have a hard cap, as you would under S. 556, requiring emission reductions at a specific source does not reduce the overall level of pollution, it just limits industrys flexibility about where to make the reductions. 