A solution is saturated with respect to ${\mathrm{SrCO}}_3$ and ${\mathrm{SrF}}_2$. The $\left[{\mathrm{CO}}_3^{2-}\right]$ was found to be $1.2\times {10}^{-3} \mathrm{M}$

The concentration of' ${\mathrm{F}}^{-}$ in the solution would be

(Given: $K_{\mathrm{sp}}\left({\mathrm{SrCO}}_3\right)=7.0\times {10}^{-10}{\mathrm{M}}^2$ and $K_{\mathrm{sp}}\left({\mathrm{SrF}}_2\right)=7.9\times {10}^{-10}{\mathrm{M}}^3$)