determine the minimum concentration of the precipitating agent on the right to cause the precipation of the cation from the solutiuon on the left.

determine the minimum concentration of the precipitating agent on the right to cause the precipation of the cation from the solutiuon on the left. 4.0×10^-2 M BaNO3; NaFI do not want an answer as much as I really just want to know how to approach the problem - my textbook is rather sparse, and I've never seen a problem like this. thank you