Calculus
posted by Jessica .
The fuel efficiency, E, in litres per 100 km, for a car driven at speed v, in km/h is E(v)=1600v/(v^2+6400)
a)If the speed limit is 50 km/h, determine the legal speed that will maximize the fuel efficiency.
Could someone explain to me why the legal speed is 50 km/h to maximize the fuel efficiency with calculations and explanations? My teacher it cannot be 50.

sorry  government regulations follow no logic which makes sense.