Problem 3 [20 Points] A vertical curve has an entrance grade of 4.2% and an exit grade of - 3.2%. The PVC of the curve is located at station 65 29.94 at an elevation of 871.73-ft. A 54-in diameter concrete pipe located at station 70 12.43 has an invert elevation of 874.51-ft. The concrete pipe has a 3-in thickness wall and requires a cover of at least 5-ft. a) Determine the minimum length of a curve that satisfies this requirement. b) The station of the highest point on the curve. c) The elevation of the highest point of the curve. d) The station of PVC.