4. (3 pts) The amount of copper in a natural water sample was determined by anodic stripping voltammetry. A 10.0 mL water sample was analyzed, resulting in a peak current resporee of 549 nA. The water sample was then spiked with 1.00 mL of a 1000. ng/mL Cu respon standard. The resulting solution was analyzed, resulting in a peak current of 7874 after Spike nA. Determine the concentration of copper in the natural water sample. (answer = 173 ng/mL) Using: