The distance between two slits in Young's double slits experiment...

The distance between two slits in Young's double slits experiment is $\mathrm{d}=2.5 \mathrm{~mm}$ and the distance of the screen from the plane of slits is $D=120 \mathrm{~cm}$. The slits are illuminated with coherent beam of light of wavelength $\lambda=600 \mathrm{~nm}$. The minimum distance (from the central maximum) of a point where the intensity reduces to $25 \%$ of maximum intensity is