Which of the following is the general trend on a world isothermal map

Temperature decrease from the tropics toward the pole

  concave means having an outline or surface that curves inward like the interior of a circle or sphere. so the mirror curves inward.

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.