Which group of items all contain a transparent part with at least one curved surface to refract light?
an owl's eye, a smart phone, and a magnifying glass
a microscope, a camera, and a window pane.
a human eye, a diving mask, and a telescope
an electron microscope, safety goggles, and eyeglasses

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.