$($b$)$ It is estimated that $80$ grams$/$sec of sulphur dioxide is being emitted from a

petroleum refinery from an average effective height of $60m$ at $8$ am on an

overcast winter morning with the surface wind $6\frac{m}{sec}.$ what is the ground level

concentration downward but at a distance $50m$ from $x-$axis from the refinery at

a distance of $500m?$