A rectangular surcharge $(3$ m x $4$ m$)$ is to be constructed at a depth of $2$ m$.$ Groundwater table is located at $1\mathrm{.}5$

m below the ground surface. Soil profile is given in the figure.

$($a$)$ Calculate the void ratio and unit weight of each soil layer.

$($b$)$ Calculate the total and effective vertical stresses and porewater pressure at point A and point B$.$

$($c$)$ Calculate the vertical stress increase due to rectangular loads at the center of each sublayer in clay using

approximate method.

$($d$)$ Calculate the total primary consolidation settlement in the bottom clay layer.