I took a test yesterday that had a question that kind of stumped me need a little help here. It went like An electric furnace that was 240v and rated at 10000va output that was going to be fed by a 208v system what would be the va output of the furnace? it was multiple choice some of the answers were something like 7500, 7600, 6900, or 5400. Anybody have an idea and how do you get that?