$11\mathrm{.}5\mathrm{.}3.$ Build a $\backslash (2$ S $/\backslash$Delta t$+$O $\backslash )$ versus $\backslash ($ O $\backslash )$ relationship in half$-$foot increments for an underground cistern that is $2$ ft deep, $6$ ft long, and $3$ ft wide. A $6-$in$-$diameter drain on the side of the cistern acts as an orifice with a discharge coefficient of $0\mathrm{.}6.$ The invert of the drain is at the bottom of the cistern. Assume a routing interval of $10$ s $.$ A spreadsheet program may prove helpful.

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