The sound emitted by bats has a wavelength of 4.38 mm. what is the frequency in air? the speed of sound in air is 343 m/s.

The frequency of a wave is equal to the linear speed divided the wavelength. so in equation form.
f = v / l
where f is the frequency
v iss the linear speed
l is the wavelength

f = ( 345 m/s ) / ( 4.38 mm ) ( 1 m / 1000 mm )
f = 78767 per second

From negative to negative

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.