Question $3$: $(35)$ The soil profile at a project site is shown.

a$)$ If the water table rises to the top of the ground surface during a flooding event, what is the change in the effective stress at the bottom of the clay layer? $(20)$

b$)$ How many meters must the groundwater table rise to decrease the effective stress by $15k\frac{N}{m^2}$ at the bottom of the clay layer? $(15)$