An industry with an effective stack height of $80 \mathrm{~m}$ emits $1200 \mathrm{~g} / \mathrm{h}$ of $\mathrm{CO}$. The windrose plotted using the meteorological data at the top of the stack, and the relation between dispersion coefficients and wind direction are given below:
\begin{array}{|l|c|c|}
\hline \multirow{2}{*}{ Wind Direction } & \multicolumn{2}{|c|}{ Dispersion coefficients (in m) } \\
\cline { 2 - 3 } & Crosswind direction & Vertical direction \\
\hline Northeast & 50 & 20 \\
\hline North & 45 & 30 \\
\hline Northwest & 40 & 35 \\
\hline East & 45 & 30 \\
\hline Southeast & 55 & 35 \\
\hline South & 60 & 40 \\
\hline Southwest & 65 & 45 \\
\hline West & 70 & 50 \\
\hline
\end{array}
During the maximum duration of the year, the ground level $\mathrm{PM}_{2.5}$ concentration at the downwind distance of $2 \mathrm{~km}$ (at the plume centerline) from the stack is _________ (in $\mu \mathrm{g} / \mathrm{m}^{3}$, $\text{rounded off to two decimal places).}$
