To a Saturated Solution of Barium Carbonate Is Added Just

To a saturated solution of barium carbonate is added just enough sodium sulfate to achieve a maximum sulfate concentration without precipitation of barium sulfate. If no complexes form and the "salt effect" is negligible, what is the concentration of the sulfate ion in this solution? [Ksp for barium carbonate is 1.6 × 10^-9; Ksp for barium sulfate is 7.9 × 10^-11]

A) 2.8 × 10^-5 M
B) 6.7 × 10^-6 M
C) 2.0 × 10^-6 M
D) 4.0 × 10^-5 M
E) 8.9 × 10^-5 M