Electrochemistry · Molar conductivity degree of dissociation

Molar conductivity of a weak acid HQ of concentration 0.18 M was found to be 1/30 of the molar conductivity of another weak acid HZ with concentration of 0.02 M. If $\lambda^{0}_{\mathrm{Q}^-}$ happened to be equal with $\lambda^{0}_{\mathrm{Z}^-}$, then the difference of the $\mathrm{p}K_\mathrm{a}$ values of the two weak acids ($\mathrm{p}K_\mathrm{a}(\mathrm{HQ})-\mathrm{p}K_\mathrm{a}(\mathrm{HZ})$) is (Nearest integer).

[Given : degree of dissociation ($\alpha$) $\ll 1$ for both weak acids, $\lambda^\circ$ : limiting molar conductivity of ions]