Above is the watershed for the Congo River. Using a reasonable estimate, what is the areawithin the watershed $($km$2)?$

b$)$If the entire watershed started out at $10\%$ impervious area, what would be the increase intotal nitrogen load $($kg$)$ if development added another $25\%$ impervious area? Use theSimple Method $($even though this watershed is greater than $2\mathrm{.}5$ km$2).$ Assume that theannual rainfall is $2,800$ mm in one$-$quarter of the watershed and $1,500$ mm in the otherthree$-$quarters, but that the development is evenly distributed.