A certain power station produces an electrical output of 700 MW, operating at 42% efficiency. This plant uses a closed-circuit "dry" cooling system in which heat is expelled by cycling the cooling water through pipes which are in direct contact with air taken in from outside the plant. The fuel for the plant is lignite, which has a typical energy content of 15 MJ/kg.
a) What is the mass of lignite consumed in 1.00 hour of operation of the plant?
b) If the cooling water operates between a temperature of 90°C and a temperature of 30 °C, what mass of water must be cycled through the cooling system in 1.00 hour?