Intense white light is incident on a diffraction grating that has $674$ lines$/$mm$.($a$)$ What is the highest order in which the complete visible spectrum can be seen with this grating? $($Enter $1$ for first order, $2$ for second order, etc.$)($b$)$ What is the angular separation between the violet edge $(400$ nm$)$ and the red edge $(700$ nm$)$ of the first order spectrum produced by the grating? $\backslash$deg