In one cycle, a Carnot engine takes in 8.00 × 10^4 J of heat and does 2.68 × 10^4 J of work. The temperature of the engine's cold reservoir is 25.0 °C. What is the efficiency of this engine?

A) 10.0%
B) 20.0%
C) 30.0%
D) 40.0%