A Carnot Engine Operating Between Reservoirs at 500 $\degree$ C and 300

Multiple Choice

A Carnot engine operating between reservoirs at 500 $\degree$ C and 300 $\degree$ C would have an efficiency of approximately

A) 0.11.
B) 0.30.
C) 0.50.
D) 0.67.
E) 0.74.