Plot vertical $($normal$)$ vs$.$ shear stress on the Mohr$-$Coulomb failure envelope. By

plotting the strength envelope to determine $($assume $c=0).$ You have to put in

your mind that, vertical $($normal$)$ stress is close to $25$kPa. To plot the normal vs$.$

shear stress graph, you have to take the values of $50$ and $100$kPa for normal

stresses, and $36\mathrm{.}28$ and $76\mathrm{.}72$kPa for peak shear stresses, respectively.