$(3)$ A $2-$ tt high retaining wall has backfill of granular soil with an angle of internal friction of $30$ and a is $\frac{125}{f}{t}^3.$ The Rankine passive lateral earth force per unit length $(($:$l\frac{b}{f}t\}$ on the wall is most nearly:

$($A$)2250$

$($B$)9,000$

$($C$)18,000$

$($D$)27,000$

Answer: $q,$

$(4)$ The stability of a slope, as shown, is to be analyzed by the ordinary method of slices. On a particular trial curved surface through the soil mass. The following information of each slice are tabulated as follows:

$\backslash$table$[[$Slice Number,$W_{n}sin{}_n(l\frac{b}{f}t),W_{n}cos{}_n(l\frac{b}{f}t)$