$1\mathrm{.}4$ Five million gallons perday $($MGD$)$ of a conservative substance, with conen $10\mathrm{.}0m\frac{g}{L},$ is released into a stream having an upstream flewr of $10\mathrm{.}0$ MGD and substance concen of $3\mathrm{.}0m\frac{g}{L}.$ Assume complete mixing

$($a$)$ What is the concen in Ppm just downstream?

$($b$)$ What is the mass rate of the substance in $k\frac{g}{?}$ day passing just downstream of the junction? Note: $1\mathrm{.}0m^3=264$gal.