Which of the following is a sparingly soluble salt?

$Mg(OH)_2$ is precipitated when $NaOH$ is added to a solution of $Mg^{2+}$. If the final concentration of $Mg^{2+}$ is $10^{-10} \ M$,the concentration of $OH^{-} \ (M)$ in the solution is (Given: Solubility product for $Mg(OH)_2 = 5.6 \times 10^{-12}$)

If the solubility product of $PbS$ is $8 \times 10^{-28}$,then the solubility of $PbS$ in pure water at $298 \ K$ is $x \times 10^{-16} \ mol \ L^{-1}$. The value of $x$ is $\dots$.
[Given $\sqrt{2} = 1.41$]

The solubility product constants of $Ag_{2}CrO_{4}$ and $AgBr$ are $1.1 \times 10^{-12}$ and $5.0 \times 10^{-13}$ respectively. Calculate the ratio of the molarities of their saturated solutions.

Calculate the solubility in $mol \ dm^{-3}$ of sparingly soluble salt $BA$ if its solubility product is $4.9 \times 10^{-13}$ at the same temperature.

Solubility of $AgCl$ in $0.2 \, M \, NaCl$ is $x$ and that in $0.1 \, M \, AgNO_3$ is $y$. Then which of the following is correct?