Correct Answer - Option 2 : 66.67

__Concept: __

- Carnot engine is a theoretical engine that operates on an ideal theoretical cycle called the Carnot cycle
- The efficiency of a heat engine is defined as the ratio of work output divided by heat input and is given by

\(η = 1 - \frac{T_{2}}{T_{1}}\) or \(η = 1 - \frac{Q_{2}}{Q_{1}}\)

Where T2 =Temperature of the sink, T1= Temperature of the source, Q1 = Heat absorbed from the source, Q2= Heat rejected to the sink

__Calculation:__

**Given:**

Q1 = 1800 kJ and Q2 = 600 kJ

- The efficiency of the heat engine is given by

\(\Rightarrow η = 1 - \frac{Q_{2}}{Q_{1}}\)

Substituting the given values in the above equation

\(\Rightarrow η = 1 - \frac{6000}{1800}=1-\frac{1}{3}=\frac23=0.67\)