)(10 points) an equal-tangent sage curve has its pvi at station 10+00 and elevation at 138 ft. directly above the pvi, the bottom of an overpass structure is at elevation 162 ft. the pvc is at station 4+00. if the initial grade is -4%, what is the highest possible value of the final grade given that a 70 mph design speed is to be provided in daytime condition? what is the highest possible final grade i nighttime conditions? (ignore the cross-sectional width of the overpass)