A concrete foundation has a length of 4.8 m, a width of 3 m and is buried at a depth of 1.8m. The additional vertical stress at the bottom of the foundation is 170 kPa. A normally consolidated clay soil layer with a 1.2 m thickness is now under the foundation and above bedrock. The clay has a unit weight of 18 kN/m 3 void ratio of 0.8, Young's modulus of 7.2 MPa. What is the final settlement (mm) of the clay layer?