Atoms And Nuclei

Consider that an electron is revolving in an excited state of Hydrogen atom with velocity $\sqrt{25.6} \times 10^5 \mathrm{~ms}^{-1}$. The radius of the orbit is $x \times 10^{-9} \mathrm{~m}$. The value of $x$ is:

[Take the mass of electron to the $9 \times 10^{-31} \mathrm{~kg}$, charge of electron $=-1.6 \times 10^{-19} \mathrm{C}$ and $\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \mathrm{Nm}^2 \mathrm{C}^{-2}$ ]