A stock solution containing Mn2 ions was prepared by dissolving 1.269 g pure manganese metal in nitric acid and diluting to a final volume of 2.000 L. The following solutions were then prepared by dilution: For solution A, 40.00 mL of stock solution was diluted to 1500.0 mL. For solution B, 10.00 mL of solution A was diluted to 250.0 mL. For solution C, 20.00 mL of solution B was diluted to 550.0 mL. a Calculate the concentration of the stock solution.