A Carnot engine operates with a large hot reservoir and a much smaller cold reservoir. As a

Question:

A Carnot engine operates with a large hot reservoir and a much smaller cold reservoir. As a result, the temperature of the hot reservoir remains constant while the temperature of the cold reservoir slowly increases. This temperature change decreases the efficiency of the engine to 0.70 from 0.75. Find the ratio of the final temperature of the cold reservoir to its initial temperature?