$($a$)$ An unstable rock block or $64t$ is at an inclination of $70$ to the horizontal and a joint plane is present at its base. The contact area of the block is $38m^2$ and the core samples of this rock have given $c=1\mathrm{.}5\frac{t}{m}2$ and $=36.$ The water pressure at the base of block$=0\mathrm{.}50\frac{t}{m}2.$ Calculate the factor of safely. In order to increase the factor of safety to $1\mathrm{.}3,$ calculate the anchor force to be supplemented normal to the block. Also find the anchor force without water pressure.