Final answer:
The maximum efficiency of a heat engine operating between hot and cold reservoir temperatures can be calculated using the Carnot efficiency formula. In this case, the maximum efficiency is approximately 69.2%.
Step-by-step explanation:
The maximum efficiency of a heat engine operating between the given hot and cold reservoir temperatures can be calculated using the Carnot efficiency formula: Efficiency = 1 - (Tc/Th). Where Tc is the cold reservoir temperature in Kelvin and Th is the hot reservoir temperature in Kelvin.
Converting the given temperatures to Kelvin, we have Tc = 27.0°C + 273.15 = 300.15K and Th = 700°C + 273.15 = 973.15K. Plugging these values into the formula, we get:
Efficiency = 1 - (300.15/973.15) = 69.2%
Therefore, the maximum efficiency of the heat engine operating between the given temperatures is approximately 69.2%.