A complete mixed activated sludge process is operated with a clarifier and sludge recycle. The influent soluble BOD concentration is $200$ mg$/$L and the flow is $1000$ m$3/$day$.$ The effluent soluble BOD is $20$ mg$/$L and the effluent VSS concentration is $40$ mg$/$L$.$ The sludge parameters are as follows:

$$m $=3$ d$-1.$ Ks $=20$ mg$/$L$,$ kd $=0\mathrm{.}1$d$-1,$ Y $=0\mathrm{.}5$ g VSS$/$g BOD

What is the oxygen demand $($in kg$/$d$)$ of the aeration tank in kg$/$d$?$