On an overcast day a stack with an effective height of $80m$ releases sulfur dioxide at $80\frac{g}{s}.$ The wind speed is $6\frac{m}{s}.$ The stack is located in a rural area. Determine

a$)$ The mean concentration of $S{O}_2$ on the ground is $400m$ downwind.

b$)$ The mean concentration on the ground is $400m$ downwind and $60m$ crosswind.

c$)$ The location and value of the maximum mean concentration on ground level directly downwind.