According to Bohr's atomic theory which of the following is correct ?

Potential energy of electron $\propto \frac{{\mathrm{Z}}^2}{{\mathrm{n}}^2}$

he product of velocity of electron and principle quantum number (n) $\propto$ Z²

Frequency of revolution of electron in an orbit $\propto \frac{{\mathrm{Z}}^2}{{\mathrm{n}}^3}$

coulombic force of attraction on the electron $\propto \frac{{\mathrm{Z}}^2}{{\mathrm{n}}^2}$