Aheat engine operates between thermal reservoirs of 1000k and 400k. it receives heat at a rate of 200 kw and rejects it at a rate of 90 kw a)- what is it's thermal efficiency b)- what is the maximum possible thermal efficiency?

Water at the rate of 1 kg/s is forced through a tube with a 2.5 cm inner diameter. the inlet water temperature is 15°c, and the outlet water temperature is 50°c. the tube wall temperature is 14°c higher than the local water temperature all along the length of the tube. what is the length of the tube?