A rapid$-$mix basin is designed for a flowrate of $15$ MGD$,$ and a hydraulic retention time of $0\mathrm{.}15$min. The basin is $2\mathrm{.}0m$ wide, $2\mathrm{.}0m$ long. If the mixer is powered with $50HP$ and the water is $20C,$ calculate the depth of the reactor and the mixing intensity, in s ${?}^{-1}).$