Please answer this and explain how you did it

It was proven that no cyclical process operating between two heat baths at temperatures TH and TC could be more efficient than the Carnot cycle. (v) What are the critical properties of the Carnot cycle that facilitate this proof? [Mark: 5 percent] (vi) Can this proof be extended to other cycles? If so, what type of cyclic processes, if not, why not? [Mark: 5 percent]