The critical slip circle for a slope is shown below along the soil properties. The length of the arc of the slip circle is $15\mathrm{.}6m$ and the area of soil within the slip circle is $82m^2.$ The radius of the slip circle is $10\mathrm{.}3m.$ Determine the factor of safety against the slip circle failure. Note failure surface is circular here. $(10$ points$)$

$=0$

$C_u=30$kpa

$=20k\frac{N}{m^3}$