2022 IIMC keystage3-IWYMIC individual Question 15

Let $\overline{abcd}$ be a four-digit number, where $a,c\ne0$, such that $\frac{\sqrt{\overline{abcd}}}{\sqrt{\overline{ab}}+\sqrt{\overline{cd}}}$ is a rational number. Find all possible value(s) of $\overline{abcd}$.