Determine the peak concentration $($mg$/$l$)$ and the time $($min$)$ for an accidental spill of $20\mathrm{.}0$ kg of atrizine to pass an irrigation intake $3\mathrm{.}0$ km downstream of the spill. $$Report also the width of the concentration cloud when the center$-$of$-$mass passes the intake. $$The spill occurs in a creek of width $15\mathrm{.}0$ m and normal depth $1\mathrm{.}5$ m when the flow rate was $15\mathrm{.}1$ m$^3/$s$.$The effective longitudinal diffuson coefficient is $7\mathrm{.}37$ m$2/$s$.$Assume the atrizine is in liquid form and that the spill is well$-$mixed across the cross$-$section by the time it reaches the intake.