Atoms and Nuclei: JEE Main 2024 Physics question

Radius of a certain orbit of hydrogen atom is 8.48 $\mathop A\limits^o$. If energy of electron in this orbit is $E / x$. then $x=$ ________ (Given $\mathrm{a}_0=0.529$ $\mathop A\limits^o$, $E=$ energy of electron in ground state).