$(5\mathrm{.}0$ points, show your work$)$ The

calibration curve shown, for copper ions

$(C{u}^{2+}),$ was constructed by measuring the

absorbance of four standard $C{u}^{2+}$ solution.

Then $8\mathrm{.}0mL$ of an unknown $C{u}^{2+}$ sample

was diluted to a total volume of $50\mathrm{.}0mL$

and the absorbance of the prepared diluted

sample solution was $0\mathrm{.}40.$

a$.(2\mathrm{.}5$ points$)$ Knowing that the density of the solution is $1\mathrm{.}00\frac{g}{m}L,$ and the molar mass of $Cu=63\mathrm{.}55$

$\frac{g}{m}ol,$ what is the molar concentration in the original $8\mathrm{.}0mL$ solution?

b$.(2\mathrm{.}5$ points$)$ What is the mass $($in $mg)$ of copper in the $8\mathrm{.}0mL$ sample?