A 25.0 mL sample of waste water is obtained to analyze for Pb2+ ions. This sample is evaporated to d — Laboratory Chemistry Question

A 25.0 mL sample of waste water is obtained to analyze for Pb²⁺ ions. This sample is evaporated to dryness and redissolved in 2.0 mL of H₂O, mixed with 2.0 mL of a buffer solution and 2.0 mL of a solution of dithizone then diluted to 10.0 mL. The absorbance of the colored Pb²⁺-dithizone complex is compared with the Beer^-Lambert plot below.
The absorbance of a portion of the final solution is 0.13. What is the concentration of Pb²⁺ ions in the waste water in ppm?