Consider the heat engine in Problem 10.47. The exit temperature was given as 800 K, but what

Question:

Consider the heat engine in Problem 10.47. The exit temperature was given as 800 K, but what are the theoretical limits for this temperature? Find the lowest and the highest, assuming that the heat transfers are as given. For an exit temperature that is the average of the highest and lowest possible, find the first and second-law efficiencies for the heat engine.