A solution contains 2.0 × 10^–3 M Ba^2+ and 1.0 × 10^–2 M Sc^3+. A source of F^– is slowly added to the solution. Will BaF2 (Ksp = 1.84 × 10^–7) or ScF3 (Ksp = 5.81 × 10^–24) precipitate first?

I believe that ScF3 would precipitate first but I don't know how to prove this mathematically.