Consider two coherent monochromatic (wavelength `lambda`) sources `S_(1) and S_(2)` separated by a distance d. The ratio of intensity of `S_(1)` and that of `S_(2)` at point P is 4. The distance of P from `S_(1)` if the resultant intensity at point P is equal to `(9)/(4)`, times the intensity due to `S_(1)` is : (n is a positive integer )

A. `(d^(2)-n^(2)lambda^(2))/(2nlambda)`

B. `(d^(2)+n^(2)lambda^(2))/(2nlambda)`

C. `(n lambdad)/(sqrt(d^(2)-n^(2)lambda^(2))`

D. `(2n lambdad)/(sqrt(d^(2)-n^(2)lambda^(2))`