In Water Saturated with BaF₂ at a Particular Temperature, the Equilibrium

In water saturated with BaF₂ at a particular temperature, the equilibrium concentration of fluoride ions is 1.5×10 ^{- 2} M . What is the K _sp of barium fluoride?

A) 1.7×10 ^{- 6}
B) 2.2×10 ^{- 4}
C) 9.0×10 ^{- 4}
D) 3.4×10 ^{- 6}
E) 4.6×10 ^{- 10}