$)$

Find the angle in degrees between the first minima for the two sodium vapor lines, which have wavelengths of $589\mathrm{.}1$ and $589\mathrm{.}6$ nm$,$ when they fall upon a single slit of width $1\mathrm{.}90$m$.$

$$

$($b$)$

What is the distance in mm between these minima if the diffraction pattern falls on a flat screen $1\mathrm{.}70$ m from the slit?

mm