A 12 ft by 24 ft rectangular shaft is sunk to a depth of 3,000 ft in ground where the premining stress field is given by formulas Sv = 1.2h, Sh = 120 + 0.5h, SH = 3, 240 + 0.3h, where h is depth in feet and the stresses are in psi. Show by sketch, the best orientation of the shaft relative to the directions of h and H. Is this the best orientation at all depths to 3,000 ft? If mine expansion plans call for two additional shafts of the same size, show by sketch the position and orientation of these additional shafts. Explain.