A 5.3 m thick unit of sand lays above a 4.9 m thick unit of clay. The water table is situated within the sand unit, 3 m below ground surface. The sand has a wet density of 1910 kg/m³ and a saturated density of 2050 kg/m³. The clay has a saturated density of 1859 kg/m³. Determine the effective stress (in kPa) at the base of the clay unit. Provide your answer to 2 decimal places without the units.