A Carnot heat engine runs between a cold reservoir at temperature TL and a hot reservoir at temperature TH. You want to increase its efficiency. Of the following, which change results in the greatest increase in efficiency? The value of AT is the same for all changes. O Raise the temperature of the hot reservoir by AT O Raise the temperature of the cold reservoir by AT O Lower the temperature of the hot reservoir by AT O Lower the temperature of the cold reservoir by AT O Lower the temperature of the hot reservoir by (1/2)AT and raise the temperature of the cold reservoir by (1/2)AT