I don\'t even know where to begin.... any help isappreciated!! At a steam power

Question

I don't even know where to begin.... any help isappreciated!!
At a steam power plant, steam engines work in pairs, theoutput of heat from one being the approximate heat input of thesecond. The operating temperatures of the first are 626°C and438°C, and of the second 410°C and 272°C. If the heatof combustion of coal is 2.80E+7 J/kg, at what rate must coal beburned if the plant is to put out 1000 MW of power? Assume theefficiency of the engines is 61.1 percent of the ideal (Carnot)efficiency. I don't even know where to begin.... any help isappreciated!!
At a steam power plant, steam engines work in pairs, theoutput of heat from one being the approximate heat input of thesecond. The operating temperatures of the first are 626°C and438°C, and of the second 410°C and 272°C. If the heatof combustion of coal is 2.80E+7 J/kg, at what rate must coal beburned if the plant is to put out 1000 MW of power? Assume theefficiency of the engines is 61.1 percent of the ideal (Carnot)efficiency.

Explanation / Answer

1000 MW = 1 * 10E9 J/s 1 * 10E9 / 2.8 * 10E7 = 35.7 kg / sec    if the engines were 100 % efficient Using 626 C = 899 K   as the high temperaturereservoir and     272 C = 545 K   as thelow temperature reservoir e = (899 - 545) / 899 = .394     theCarnot efficiency .611 * .394 = .241   the working efficiency of theengines Thus R = 35.7 / .241 = 148 kg / sec    rate which coal must be burned

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