Light consisting of plane waves of wavelength $\lambda_1 = 8\times10^{-5}$ cm and $\lambda_2 = 6\times10^{-5}$ cm generates an interference pattern in Young's double slit experiment. If $n_1$ denotes the $n_1$th dark fringe due to light of wavelength $\lambda_1$ which coincides with $n_2$th bright fringe due to light of wavelength $\lambda_2$, then