In a stormwater management project, an engineer is evaluating the performance of a storm drain tunnel with a semicircular cross$-$section. During a severe storm event, the water surface level within the tunnel rises to $2\mathrm{.}5$ meters above the top of the semicircular section. The Manning's roughness coefficient $($ n $)$ for the tumnel is $0\mathrm{.}02,$ and the slope of the channel is $0\mathrm{.}009,$ what is the calculated discharge rate of the storm drain tunnel? $(5$ points$)$