4. An oil rig is located 5 miles offshore, and a town is located 6 miles down the coast from the oil rig. A company is hired build a pipe from the oil rig to the town. It costs $6000 per mile to run pipe underwater and $4000 per mile to run pipe on land. Find the most economical path to lay the pipe from the oil rig to the town. 5. Find the point on the parabola y = x which is the closest to the point (10,2). 6. An open box is to be made from a square piece of material, 10 inches on a side, by cutting equal squares from each corner and folding up the sides. Find the volume of the largest box that can be made