Wave Optics

In a Young's double slit experiment, the intensities at two points, for the path difference $\dfrac{\lambda}{4}$ and $\dfrac{\lambda}{3}$ ($\lambda$ being the wavelength of light used) are $I_1$ and $I_2$ respectively. If $I_0$ denotes the intensity produced by each one of the individual slits, then $\dfrac{I_1 + I_2}{I_0} = $
$\left(\cos 45^\circ = \dfrac{1}{\sqrt{2}}, \cos 60 = \dfrac{1}{2}\right)$