They are using temperature and that is throwing me off. My books examples use Watts for the High and low temp sources, so in this case, I don't know how to relate it. Please show me.
A 2-GW steam power plant, which uses a nearby river as a low-temperature sink, has an actual thermal efficiency of 55 percent. The high-temperature source is a 400 degree celcius boiler, and the temperature of the river water is 10 degrees celcius. Find the rate of heat transfer to the river and the ideal thermal efficiency of the power plant.