Remember that a measured value agrees with an established value if the established value is within a range of +2deltaX of the measures mean, where DeltaX is the standard uncertainty. Which of the materials shown above might the cylinder be?

You get 6 for mechanical

If the heat engine is a perfect carnot cycle engine, thenefficiency = (t2-t1)/t2   where t1=temperature of cold reservoir ( ° k) = 135            t2=temperature of hot reservoir ( ° k)   = 325thereforeefficiency = (t2-t1)/t2 = (325-135)/325 = 0.5846 = 58%  note: this is the theoretical maximum efficiency of a perfect heat engine.   real-life engines do not achieve this value.