$\Rightarrow s_{1}=\sqrt{K_{s p}}=\sqrt{6.2 \times 10^{-13}}$
$=7.87 \times 10^{-7} \mathrm{mol} \mathrm{L}^{-1}$
For $N Y_{3}: K_{s p}=27 s_{2}^{4}$
$\Rightarrow s_{2}=\sqrt[4]{\frac{6.2 \times 10^{-13}}{27}}$
$=3.89 \times 10^{-4} \mathrm{mol} \mathrm{L}^{-1}$
Hence, molar solubility of $MY$ in water is less than that of $NY_3$ .