Which of the following has the maximum solubility? (Given $K_{sp}$ values)

Assign $A, B, C, D$ from the given type of reaction.
$SrC_2O_4(s) + 2HCl(aq) \longrightarrow SrCl_2(aq) + H_2C_2O_4(aq)$

Solubility of $PbI_2$ is $0.005 \ M$. Then,the solubility product of $PbI_2$ is

For the following Assertion and Reason,the correct option is
Assertion $(A) :$ When $Cu^{2+}$ and sulphide ions are mixed,they react together extremely quickly to give a solid.
Reason $(R) :$ The equilibrium constant of $Cu^{2+}_{(aq)} + S^{2-}_{(aq)} \rightleftharpoons CuS_{(s)}$ is high because the solubility product is low.

The solubility products $(K_{sp})$ of three sparingly soluble salts $M_2X$,$MX$,and $MX_3$ are identical. What will be the order of their solubilities $(s)$?

$A_{3}B_{2}$ is a sparingly soluble salt of molar mass $M \ g \ mol^{-1}$ and solubility $x \ g \ L^{-1}$. The solubility product satisfies $K_{sp} = a(\frac{x}{M})^{5}$. The value of $a$ is ...... . (Integer answer)