In an aqueous solution of \( CaF_2 \) , the concentration of \( F^- \) ion is \( 6.55 \times 10^{-3} \text{ gL}^{-1} \) , what is the solubility product of \( CaF_2 \) ?

A \( 2.68 \times 10^{-12} \)

B \( 3.87 \times 10^{-11} \)

C \( 2.05 \times 10^{-11} \)