89. Solving a chemistry problem

When determining lead in 10.0 ml of waste water, a Pb (II) peak 75 mm high was observed on the voltammogram. 0.50 ml of a standard 2.0 * 10-4 M Pb (II) solution was added to the analyzed solution, and the voltammogram was recorded again. The height of the peak has grown to 163 mm. On the background polarogram (0.1 M HNO3), a peak 11 mm high was observed. Calculate the lead content (mg/l) in the waste water.