A three-compartment rectangular shaft 12 × 24 ft in cross section is planned for a depth of 3,000 ft. The pre-sinking stress field is assumed to be caused by gravity only. The weakest rock along the proposed shaft route has an unconfined compressive strength of 8,000 psi and a tensile strength of 750 psi. Young’s modulus and Poisson’s ratio are estimated to be 4.5 million psi and 0.25. Specific weight of rock is 162pcf. Determine the safety factors, with respect to tension and compression. What is the optimum orientation of the shaft?