In the YDSE apparatus shown the ratio of maximum to minimum intensity on screen is 9. The wavelength of light used is $\lambda$, the value of y is :

Question

$(a)\;\frac{\lambda D}{3d} \\ (b)\;\frac{\lambda D}{d} \\ (c)\;\frac{3 \lambda p}{d} \\ (d)\;\frac{2 \lambda D}{3d} $