A consolidation test was performed on a $1\mathrm{.}2-$inch$-$thick clay sample, drained on both sides, and taken from the mid$-$stratum $($i$.$e$.,$ at a depth of $13ft)$ of the clay layer shown in the figure below. It took $7\mathrm{.}5$ minutes to achieve $65\%$ of primary consolidation. Other parameters are shown in the figure below. Answer the following questions $(100$ points$)$:

a$.$ Find the final settlement of the clay layer below the centerline of the levee. Use the stress at the center of the clay layer $($i$.$e$.,$ at a depth of $13ft)$ as a representative value of the stress of the entire layer.

b$.$ Find the final settlement of the clay layer below the toe of the levee. Again, use the stress at the center of the clay layer $($i$.$e$.,$ at a depth of $13ft)$ as a representative value of the stress of the entire layer.

c$.$ Find the time required to reach $90\%$ of the primary consolidation of the clay layer.