$3\mathrm{.}1$ A vertical cut has been excavated, with a joint plane mapped as indicated in the sketch

below:

The following information is available for the joint plane:

$=30+0\mathrm{.}58{}_n(kPa),$

$=2700k\frac{g}{m^3},$ and

$g=9\mathrm{.}81\frac{m}{s^2}.$

Calculate the Factor of Safety by using either the forces or the stresses, and stipulating all

assumptions used for the calculations.