To solve this problem it is necessary to apply the concepts related to destructive and constructive diffraction formulated in the bragg law.
It is understood by said law that,

where,

n = Any integer, representing the repetititon of the spectrum.
d = Width
It is the angle between the incident rays and the dispersion planes.
PART A) For a diffraction of first order n=1, then




PART B) For a diffraction of second order n=2, then




Therefore the angles of the first two diffraction orders are 3.1° and 6.2°