Calculations of Ksp

a) calculate the concentrations of dissolved PbI2, Pb+2 and I-1 ions when Ksp = 1.35 x 10-9

b) calculate the Ksp of Ag3CrO4 when the concentration of silver cations is 4.16 x 10-6 mol/L when you know that this dissociation occurs: Ag3CrO4 ↔ 3 Ag+ + CrO4-3