A transparent diffraction grating has a period d = 1.50m. Find the angular dispersion D (in angular

Question:

A transparent diffraction grating has a period d = 1.50μm. Find the angular dispersion D (in angular minutes per nanometres) corresponding to the maximum of highest order for a spectral line of wavelength λ = 530 nm of light falling on the grating
(a) At right angles;
(b) At the angle θo = 45° to the normal.