Question: The Railpower GG20B "Green Goat" is powered by an item sold by what American corporation?
Sentence (from "Railpower GG20B"): The Railpower GG20B "Green Goat" is a low-emissions diesel hybrid switcher locomotive built by Railpower Technologies Corp. It is powered by a single Caterpillar C9 six cylinder inline engine developing 300 hp , which is also connected to a large battery bank where both sources combine for a total power output of 2000 hp .
Relevant evidence: Yes