A lake with a constant volume of $5\mathrm{.}0{10}^{7}L$ and surface

area of $12,000m^2$ is fed by a stream with a flow rate of

$7\mathrm{.}7\frac{m^3}{s}.$ The stream has $18\frac{g}{L}$ of dissolved arsenic. A

nearby factory dumps $1,000\frac{g}{d}$ of additional arsenic to

the lake. The arsenic settles at a rate of $0\mathrm{.}24\frac{m}{d}.$ The

lake outflow is $25\frac{m^3}{s}.$ In answering the following,

assume that the lake is well mixed.

a$)$ Find the concentration of arsenic in the lake at

steady$-$state $($in units of $\frac{g}{L})$

$\frac{g}{L}$

b$)$ What is the magnitude of the washout and settling

loss of arsenic from the lake $($in units of $k\frac{g}{d})?$ washout

$=,k\frac{g}{d}$ settling $=,k\frac{g}{d}$