Consider a watershed $($CN $=75)$ with an area of $18\mathrm{.}0$ km$2.$ From a $20$ hour storm event, the observed cumulative rainfall depth is given in the table below. Determine the excess rainfall hyetograph $[$cm$]$ and the total runoff volume $[$m$3]$ for this storm using the NRCS rainfall$-$runoff relation. You do not need to plot the hyetograph. Be careful with units.

Time$[$h$]0|4|8|12|16|20|$

Cumulative rainfall $[$cm$]0\mathrm{.}0|2\mathrm{.}1|4\mathrm{.}5|8\mathrm{.}0|8\mathrm{.}5|8\mathrm{.}5|$