7. A sag vertical curve with no passing permitted in being rebuilt on a highway in an unlit suburban area. The grade entering the curve is -6% leading into a 3.5% grade. Using the sag vertical formula from a textbook or AASHTO and a speed limit of 35 mph, what is most nearly the required length of curve. c) 130 ft; b) 250 ft; c) 500 ft; d) 1000 ft Hint: The textbook or AASHTO formula is based on headlight sight distance. Only stopping sight distance should be considered, since no passing is permitted