$(25$p$)$ A foundation $55m,$ carrying a uniform pressure of $400k\frac{N}{m^2},$ is located at a depth of $2m$ in a layer of clay $3m$ thick for which the value of $E_u$ is $60M\frac{N}{m^2}.$ The layer is underlain by a second clay layer $4m$ thick for which the value of $E_u$ is $90M\frac{N}{m^2},$ and a third clay layer $1m$ thick for which the value of $E_u$ is $110M\frac{N}{m^2}.$ A hard stratum lies below the third layer. Ground water table is at the depth of the foundation. Determine the average immediate settlement under the foundation.