There are design specifications for the minimum sight distance (distance to see an approaching vehicle measured along the roadway from the intersection of the two roadways) that a driver stopped at a stop sign must have to safely cross the roadway (not to turn onto the other roadway but to cross) where vehicles do not stop. Major roadway design speed, DS, mph Sight distance, SD, ft 25 240 30 290 35 335 40 385 45 430 50 480 60 575 65 625 70 670 75 720 (a) Plot a graph with design speed as the independent variable. (b) Determine the equation of the relationship using the method of selected points. (c) Determine the equation of the relationship using computer-assisted methods. (d) Predict the sight distance required at 55 mph.