Point A is located 3 meters under the ground surface of a saturated site where the silty soil has unit weights = 20 and 21 kN/m³, friction angle = 37 degrees, lateral stress ratio = 0.5, and cohesion intercept3 kPa. Determine the highest vertical effective stress that point A can support while the horizontal effective stress remains constant. Answer 81.5 kPa.

Fig: 1