The Gas Mileage M , in Miles Per Gallon, Obtained

The gas mileage m , in miles per gallon, obtained during a long trip is given by where s is the speed of the automobile in miles per hour and . At what constant speed can the automobile drive to obtain a gas mileage of exactly 25 miles per gallon?

A) 25 mph and 40 mph
B) 45 mph and 49 mph
C) 25 mph and 45 mph
D) 40 mph and 49 mph
E) 40 mph and 45 mph