P.3-13 The formula v2.5r models the safe maximum speed, v, in miles per hour, at which a car can travel on a curved road with radius of curvature, r, in feet. A highway crew measures the radius of curvature at an exit ramp as 810 feet. What is the maximum safe speed? A. 81 miles per hour OB. 50 miles per hour C. 42 miles per hour D. 45 miles per hour