ap-calculus-bc 2012 Q85
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The fuel consumption of a car, in miles per gallon (mpg), is modeled by $F ( s ) = 6 e ^ { \left( \frac { s } { 20 } - \frac { s ^ { 2 } } { 2400 } \right) }$, where $s$ is the speed of the car, in miles per hour. If the car is traveling at 50 miles per hour and its speed is changing at the rate of 20 miles/hour$^{2}$, what is the rate at which its fuel consumption is changing?
(A) 0.215 mpg per hour
(B) 4.299 mpg per hour
(C) 19.793 mpg per hour
(D) 25.793 mpg per hour
(E) 515.855 mpg per hour