A sample solution is to be analyzed for [Cu+2]. Three 5.0 mL aliquots are removed: to aliquot No.1 is added nothing; to No.2 is added 5?L of 100 ppm Cu+2, and to No.3 is added 10?L of 100 ppm Cu+2. (Assume negligible aliquot volume change). Signal responses for Cu+2 were: No. 1 = 0.200 units; No. 2 = 0.315 units; No.3 = 0.430 units. What is the [Cu+2] of the sample solution in ppm?