An investigation at a particular site reveald 10 m of clay overlying 2m of sand resting on bedrock.the water table was found to be at the ground surface and the piezometric level for the sand to be 2m above ground level.if the density of the clay is equal to 2.0 Mg/m3 ,calculate the total vertical stress ,pore water pressure and effective vertical stress at a depth of 5 meters below ground level.