A foundation $2m1\mathrm{.}5m$ is located at a depth of $1\mathrm{.}3$ m in a stronger clay. A softer clay is located at a depth H of $3\mathrm{.}5$ ft $,$ measured from the bottom of the foundation.

For the Top layer;

Undrained shear strength $=120k\frac{N}{m^2}$

Unit weight $=16\mathrm{.}8k\frac{N}{m^3}$

and for the bottom clay layer,

Undrained shear strength $=48k\frac{N}{m^2}$

Unit weight $=16\mathrm{.}2k\frac{N}{m^3}$

Determine the gross allowable load for the foundation with an FS of $3.$