a layer of clay, 5m thick, overlies a deposite of sand, 5m thick, which is underlaid by rock. the water table in the sand is sub-artesian with a level at 2m below fround level. the saturated unit weights of the clay and sand are 21 and 16 KN/m^3 respectively. determine the total stress, pore water pressure, and effective stress at the top and bottom of the sand.