Solubility of $CaF_2$ in a solution of $Ca(NO_3)_2$ will be represented by the concentration term?

The conductivity of a saturated solution of $BaSO_4$ is $3.06 \times 10^{-6} \ \Omega^{-1} \ cm^{-1}$ and its equivalent conductance is $1.53 \ \Omega^{-1} \ cm^2 \ eq^{-1}$. Then the $K_{sp}$ for $BaSO_4$ will be:

If the solubility product constant $(K_{sp})$ of $Ni(OH)_2$ is $1.9 \times 10^{-15}$,the molar solubility of $Ni(OH)_2$ in $1.0 \ M \ NaOH$ is:

The solubility product for a salt of the type $AB$ is $4 \times 10^{-8}$. What is the molarity of its saturated solution?

Solid $Ba(NO_3)_2$ is gradually dissolved in $1.0 \times 10^{-4} \, M \, Na_2CO_3$ solution. At which concentration of $Ba^{2+}$ will the precipitation begin? $(K_{sp} \, BaCO_3 = 5.1 \times 10^{-9})$

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$Ag_2CO_3 \downarrow + 2HCl \longrightarrow 2AgCl \downarrow + CO_2 \uparrow + H_2O$