$(25\%)$ Problem $2.$ A $6m$ thick embankment with top and side views shown in Figure P$2$ is going to be built on the ground surface. The shaded area is where the embankment is going to be built. Point $A$ is located at a depth of $4m$ underneath the ground surface below the center of the large rectangular area of the embankment $($Figure P$2).$ The embankment unit weight is $=18k\frac{N}{m^3}.$ Find the increase in the vertical stress due to the embankment at Point A$.$