A tabular ore body 15 ft thick is mined full-seam height at a depth of 2,300 ft by repeated slices 20 ft wide and 5,000 ft long, so the first drive is simply a 20 ft wide tunnel from the rock mechanics view. Rock properties are, E = 5.7 × 106 psi, v = 0.25, Co = 25,300 psi, To = 2,600 psi. The premining stress field is due to gravity alone. If safety factors of 2.2 in compression and 4.4 in tension are required, how many slices side by side can be safely taken?