In a rural area, two highways intersect. The east-west highway has no control, north-south highway has yield control. If a store located on the NW corner obstructs the view at a distance a= 45 ft (from the north-south vehicle path) and b= 90 ft (from the east-west vehicle path), and the design spee on the north-south highway is 20 mph. Required:
What is the maximum safe (design) speed on the east-west roadway?