Calculating heat gained or lost requires mass, specific heat , and
a) change in heat
b) relative humidity
c) change in temp
d) rate of temp change

Answer (d) the universe had cooled enough for atoms to combine, protons and neutrons were too far apart to form nuclei;

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.