Please help!

$12$ points CMFR$,$ no reaction. $10$ kg of contaminant is accidentally dumped

into a pond $(10,000m3).$ The pond is continuously flushed with a fresh

water stream at $200\frac{L}{m}in.$

a$.$ What is the initial contaminant concentration?

b$.$ What is the HRT$?$

c$.$ What is the concentration after $1$ HRT$?$ Ignore any reactions and

volatilization. $($You must write and solve the mass balance for credit.$)$

d$.$ What is the concentration after $1$ week?

e$.$ How long will it take to reach a "safe" concentration of $0\mathrm{.}1m\frac{g}{L}?$

f$.$ How many HRT$\text{'}$s is this?