Help needed finding the minimum ion concentration in a solution...?

It is necessary to add iodide ions to precipitate the lead(II) ions from 250 mL of 0.069 M Pb(NO3)2(aq). What minimum iodide ion concentration is required for the onset of PbI2 precipitation? The solubility product of PbI2 is 1.4 � 10^-8. Answer in units of mol/L. What m of KI must be added for PbI2 to form? Answer in units of g.