Calculus
posted by Jake .
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) Determine the legal speed speed that will maximize the fuel efficiency if the speed limit is 50 km/h.
The answer is 50 km/h but my teacher said it can't be that. Any explain please.

b) Determine the speed intervals, within the legal speed limit of 0 km/h to 100 km/h, in which the fuel efficiency is increasing.

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