The united states uses 1.4×1019 j of electrical energy per year. assume, that all this energy came from the fission of 235u, which releases 200 mev per fission event. assume that all fission energy is converted into electrical energy. part a how many kilograms of 235u would be used per year? express your answer to two significant figures and include the appropriate units. m m = nothing nothing request answer part b how many kilograms of uranium would have to be mined per year to provide that much 235u? (recall that only 0.70% of naturally occurring uranium is 235u.) express your answer to two significant figures and include the appropriate units.