Answer :
The efficiency of the heat engine is 66.67%.
Efficiency of the heat engine
The efficiency of the heat energy is determined by taking the ratio of the output energy to input energy as shown below;
[tex]\eta = \frac{0utput \ energy}{1nput \ energy} = \frac{1200}{1800} \times 100\% = 66.67\%[/tex]
Evaluation of the claim
The efficiency of the heat engine is greater than 50% but less than 75% and can be considered to be moderately efficient.
This implies that the heat engine can convert up-to two-third of the input energy into useful energy.
Learn more about efficiency here: https://brainly.com/question/15418098