An equal-tangent sag 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 -4.0%, what is the highest possible value of the final grade given that a 70 mph design speed is to be provided in daytime conditions? What is the highest possible final grade in nighttime conditions? (Be careful of units of A, and ignore x-sectional width of the overpass.