Solubility product constants (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:

2.5 mL of $$\frac{2}{5}$$M weak monoacidic base (K$$_b$$ = 1 $$\times$$ 10$$^{-12}$$ at 25$$^\circ$$C) is titrated with $$\frac{2}{15}$$M HCl in water at 25$$^\circ$$C. The concentration of H$$^+$$ at equivalence point is (K$$_w$$ = 1 $$\times$$ 10$$^{-14}$$ at 25$$^\circ$$C).