$($b$)$ The same ground anchor of part $($a$)$ above $($i$.$e$.d$ and $D$ as shown in Figure $4)$ is used in a stiff clay with $C_u=120kP{P}_a.$ Assuming $=0\mathrm{.}5$ and $N_j=9,$ determine the minimum fixed length required to resist a load of $100kN.$

D$=0\mathrm{.}2$m and d$=0\mathrm{.}1$m