A motorist traveling at 55 mph on an expressway intendeds to leave the expressway using an exit ramp with a maximum allowable speed of 30 mph. At what point on the expressway should the motorist step on her brakes in order to reduce her speed to the maximum allowable on the ramp just before entering the ramp? Assume that the coefficient of skidding friction between the tires and pavement is 0.3 and that the alignment of this section of the road is flat and level.?