Let the molar solubility of MY be $S_1$. $MY \rightleftharpoons M^+ + Y^-$ $K_{sp} = S_1 \times S_1 = S_1^2$ $S_1 = \sqrt{6.2 \times 10^{-13}} = \sqrt{62 \times 10^{-14}} \approx 7.87 \times 10^{-7} \text{ M}$

Let the molar solubility of $NY_3$ be $S_2$. $NY_3 \rightleftharpoons N^{3+} + 3Y^-$ $K_{sp} = S_2 \times (3S_2)^3 = 27S_2^4$ $S_2 = \left(\frac{6.2 \times 10^{-13}}{27}\right)^{1/4} = \left(\frac{6200 \times 10^{-16}}{27}\right)^{1/4} \approx (229.6 \times 10^{-16})^{1/4} \approx 3.89 \times 10^{-4} \text{ M}$

Comparing $S_1$ and $S_2$, we find that $S_1 < S_2$. Therefore, the molar solubility of MY in water is less than that of $NY_3$. Furthermore, the addition of KY will decrease the solubility of both salts due to the common ion ($Y^-$) effect. Thus, the other statements are false.