Explanation

(a)
$\beta$_{4} for $\left\lbrack ML_{4} \right\rbrack^{2 -}$can be written as
$\beta$_{4}=$\frac{\left\lbrack ML_{4} \right\rbrack^{2 -}}{\left\lbrack M^{2 +} \right\rbrack\left\lbrack L^{-} \right\rbrack^{4}}$ $= 2.5 \times 10^{13}$
The overall formation equilibrium constant can be written as
k=$\frac{\left\lbrack ML_{4} \right\rbrack^{2 -}}{\left\lbrack M^{2 +} \right\rbrack\left\lbrack L^{- 1} \right\rbrack^{4}}$
k=$\ \beta_{4} = 2.5 \times 10^{13}$