Ex$$ra Credit $(10$ points$)$

A new swimmite pool is being designot for a hotel in Clovis. The side retaining walls, shown in the following figure, retain bock fill soil on one side while relaining water on the other. The backfill is sandy soil with unit weight $=114l\frac{b}{t^3}$ and ${}^{\text{'}}-34.$ Assume unit weight of concrete as $150Ibf{t}^3.$

a$)$ Find the safety factor against overturning when the pool water level is at full mark.

b$),$ b$)$ The pool water level needs to be lowered for regular maintenance. Find the critical height $($F$.$S$.$ tor overturning $-1)$ of water to be maintained to prevent the wall from overturning