A shallow foundation supported by a silty sand is shown in the figure below. Estimate the elastic settlement of the foundation $($Use eq$.11\mathrm{.}20)$ given:

Length: $L=3m$

Width: $B=3m$

Depth of foundation: $D_f=1\mathrm{.}5m$

Thickness of foundation: $t=0\mathrm{.}25m$

Load per unit area: $=150k\frac{N}{m^2}$

$E_f=15{10}^{6}k\frac{N}{m^2}$

The silty sand has the following properties.

$H^{\text{'}}=20m$

${}_s=0\mathrm{.}3$

$E_O=16,000k\frac{N}{m^2}$

$k=400k\frac{N}{m^2}\frac{?}{m}$