A particular nuclear power reactor operates at 1000 MWe (megawatts electric) with an overall efficiency in converting fission energy to electrical energy of 30 percent. What mass of ²³⁵U must fission in order for the power plant to operate for 

(a) one day,

(b) one year? 

(c) If the energy were provided by burning coal instead of ²³⁵U, what would be the answers to (a) and (b)? (Burning coal produces approximately 3.15 x 10⁷ J/kg.)