You have learned of two fundamental units that are not vector quantities. which are they?

It would be Mass and Time which would be the two fundamental units.

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.

We can infer that star y is closer but other factors must be considered including the heat of the star, the mass, and the brightness of the star. even though star x seems dimmer it may just be less bright or contain less heat.