Solubility product constant ($K_{sp}$) of salts of types MX, MX$_2$ and M$_3$X at temperature $T$ are $4.0 \times 10^{-8}$, $3.2 \times 10^{-14}$ and $2.7 \times 10^{-15}$ respectively. Solubilities (mol dm$^{-3}$) of the salts at temperature $T$ are in the order