Consider an Aqueous Solution Which Is 0

Consider an aqueous solution which is 0.020 M in Pb2+ and 0.20 M in Ag+. Concentrated potassium iodide solution (so that volume changes may be neglected) is added gradually with good stirring to this solution. Eventually the iodide ion concentration should increase enough to cause precipitation of the second ion. What will be the concentration of the ion that precipitates first when the second ion just begins to precipitate?

A) 2.0 × 10^-17 M
B) 1.2 × 10^-8 M
C) 5.0 × 10^-20 M
D) 1.4 × 10^-13 M
E) 1.2 × 10^-5 M