1. In a deposit of sand ('=35), the unit weight above the water table (dry) is yd=17 kN/m, unit weight below the water table (saturated) is ysat=20.51 kN/m. if the water table is at depth of 2.5 m from the ground surface, (a) find the vertical effective stress at depth of 4m (b) Find the shear strength of soil along the horizontal Plane at depth of 4 m (c) Find the change in shear strength at depth of 4 m.