In a site consisting entirely of clays, an electric friction cone penetrometer measures the cone resistance q_c at a depth of 8.0 m as 0.75 MN/m². The water table is at 3.0 m below the ground level. The unit weights of the clay above and below the water table are 16.5 kN/m³ and 19.0 kN/m³, respectively. Estimate the undrained shear strength, preconsolidation pressure, and overconsolidation ratio at this depth.