Determine the maximum possible efficiency of the following heat engines: (a) an internal-combustion engine using the atmosphere at 20°c as the heat sink, the temperature after combustion being 1450°c, (b) a steam-cycle power station using a supercritical one-through boiler with a steam temperature of 750 c and a condensing temperature of 20°c, (c) a steam-cycle power station using a conventional dram-and-tube boiler with a steam temperature of 570c and a condensing temperature of 20"c, (d) a power station designed to work on the temperature difference in sea water, the cold temperature being 10°c and the hot temperature 22°c.