<prompt> Translate the following text to EnglishLakini bei ya gesi inaanza kuongezeka, ambayo inaruhusu makaa ya mawe kufanya kurudi kwa kiasi kikubwa kwa kuzingatia hali ya A. Hii ni kweli hasa kama teknolojia safi na ufanisi zaidi ya makaa ya mawe huanza kupenya soko kama inavyodhaniwa katika hali ya B hadi D. Ili kusawazisha mwelekeo wa uzalishaji wa makaa ya mawe kuongezeka, bei ya ruhusa inahitaji kurekebishwa juu.  <response>: But gas prices begin to rise which allows coal to make a modest comeback with respect to scenario A. This is especially true as cleaner and more efficient coal technologies begin to penetrate the market as assumed in scenarios B through D. In order to offset the tendency for coal-generated emissions to increase, permit prices need to adjust upward. 