Consider two coherent monochromatic (wavelength $\mathrm{\lambda }$ ) sources ${\mathrm{S}}_1$ and ${\mathrm{S}}_2$ separated by a distance $\mathrm{d}$. The ratio of intensity of ${\mathrm{S}}_1$ and that of ${\mathrm{S}}_2$ at point $\mathrm{P}$ is 4. The distance of $\mathrm{P}$from $S_1$if the resultant intensity at point $P$ is equal to $\frac{9}{4}$ times the intensity due to ${\mathrm{S}}_1$ is: ( $\mathrm{n}$ is a positive integer)