$7-9.$ Continuing Problem $7-7,$ test results also indicated that the coefficient of consolidation $(c_v)$ of the clay is $2\mathrm{.}18{10}^{-3}$ in$.\frac{{?}^2}{m}in$ for the pressure increment from $1$ to $2$ tons $\frac{?}{f{t}^2}.$ Compute the time of primary consolidation settlement. Take $U$ at $10\%$ increments and plot these values on a settlement$-$log time curve.