the water table is 5m below the surface but sand to a height

the water table is 5m below the surface but sand to a height

Question
in a deposit of fine sand the water table is 5m below the surface but sand to a height of 1.5m above the water table is saturated by capillary water; above this height the sand may be assumed to be dry. the saturated and dry unit weights, respectively, are 20 and 16 kN/m3.

calculate the effective vertical stress in the sand 9m below the surface.