An unknown Cu2+ sample gave an absorbance of 0.262 in an atomic absorption analysis. Then 1.00 ml of solution containing 100.0 ppm Cu2+ was mixed...

An unknown Cu2+ sample gave an absorbance of 0.262 in an atomic absorption analysis. Then 1.00 ml of solution containing 100.0 ppm Cu2+ was mixed with 95.0 ml of the unknown, and mixture was diluted to 100.0 ml in a volumetric flask. The absorbance of the new solution was 0.500. What is the concentration of Cu2+ in the sample? State any assumptions you might make and pay attention to significant figures.