Monochromatic light from two slits forms an interference pattern on a screen. At a certain point on the screen, the intensity of the interference pattern is $66\mathrm{.}0\%$ of the maximum.

$($a$)$

What is the minimum phase difference $($in radians$)$ between the light from the slits that produces this result?

rad

$($b$)$

If the wavelength of the light is $484\mathrm{.}1$ nm$,$ what is the path difference $($in nm$)$ that corresponds to this phase difference?

nm