Question $4.$

Using first principles and phase relationships, show that the unit weight of a soil $()$ is related to the void ratio $(e),$ degree of saturation $(S)$ and the specific gravity $(G_s)$ by

$=(\frac{G_s+Se}{1+e}){}_w$

From this, deduce the expressions for the dry unit weight $({}_d)$ and saturated unit weight $({}_{\text{s}\text{a}\text{t}})$