An aqueous solution of sodium fluoride is slowly added to a water sample that contains barium ion (0.0340 M) and calcium ion (0.0710 M). The Ksp of barium fluoride is 1.0 x 10^-6. The Ksp of calcium fluoride is 3.9 x 10^-11. What is the remaining concentration of the first ion to precipitate when the second ion begins to precipitate?