Astring that is 18.0 cm long and has a mass per unit length of 8.00 10-3 kg/m is stretched to a tension of 23.0 n. (a find the fundamental frequency.

It's have to be 12 or idk

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.

Iwould say the answer is d