A soil profile consists of 5 m of compacted sandy clay followed by 5 m of medium dense sand. Below the sand is a layer of compressible silty clay 20 m thick. The initial groundwater table is located at the bottom of the first layer (at 5 m below the ground surface). The densities are 2.05 Mg/m3 (ρ), 1.94 Mg/m3 (ρ sat), and 1.22 Mg/m3 (ρ') for the three layers, respectively. Compute the effective stress at a point at mid-depth in the compressible clay layer. Then, assuming that the medium dense sand remains saturated, compute the effective stress in the clay layer at midpoint again, when the groundwater table drops 5 m to the top of the silty clay layer. Comment on the difference in effective stress.?