Which from the following equations represents the relation between solubility ( $\mathrm{mol} \mathrm{L}^{-1}$ ) and solubility product for the salt $\mathrm{B}_2 \mathrm{~A}$ ?

Calculate the pOH of buffer solution formed from 0.3 M weak base and 0.45 M of its salt with strong acid $\left[\mathrm{pK}_{\mathrm{b}}=4.7447\right]$

Calculate degree of dissociation of a weak monobasic acid in 0.01 M solution if dissociation constant is $1.6 \times 10^{-5}$.