2. A 1.5 ft-thick trapezoidal shaped footing has the dimensions of 5 ft, 15.8 ft, 15 ft, and 15.8 ft (i. e., its one side is 5 ft wide, its opposite parallel side is 15 ft wide, and the distance between these opposing sides is 15 ft). It will be placed at a depth of 5 feet in soil that has a total unit weight of 130 pcf, and it will sustain a load of 160 tons (which includes the weight of footing). The footing will be placed at the bottom of a hole that will be excavated 5 feet into the ground, so you want to know the increase in stress due to the footing, which is the applied footing pressure minus the vertical stress reduction due to the excavation of the soil. Estimate the vertical stress increase due to the net applied footing pressure under the center and under a corner along the 15-ft long side of the trapezoidal combined footing described above at depths of 8 feet and 16 feet below the original ground surface.