At a steam power plant, steam engines work in pairs; the rejected heat from the first is the heat input to the second. The operating temperatures of the first are 670 C and 440 C. The operating temperatures of the second are 440 C and 290 C. Assume both engines work at 60% of their Carnot efficiency. The heat of combustion of coal is 2.8 x 10^7 J/kg. How many kg of coal must be burned per day if the power output of the plant is to be 1000 MW? I know that the QL of the first engine is the QH of the second engine, but how do I get the actual values with only the efficiency and the ratio of the temperatures?