$3\mathrm{.}28.$ A bridge has piers $2$ ft wide at $\backslash (20-\backslash$mathrm$\{$ft$\}\backslash )$ centers. A short distance upstream the depth of the river is $10$ ft and its velocity $\backslash (10\backslash$mathrm$\{$ft$\}/\backslash$mathrm$\{$sec$\}\backslash ).$ Assuming that the piers have a drag coefficient, as defined by Eq$.(1-22),$ of $($a$)1\mathrm{.}5,($b$)2\mathrm{.}0($with $\backslash ($ A $\backslash )$ and $\backslash ($ v $\backslash )$ based on the upstream flow$)$ find the depth when the flow has gone far enough downstream for the local disturbances caused by the piers to be evened out. Neglect the bed slope and bed resistance.