a. A diffraction grating is used to resolve 474.7 nm and 474.72nm light, at 3rd order. What is the minimum number of lines in thegrating? b. If the 4th order maximum is visible for this grading for474.7 nm and 474.72 nm light, what is the smallest line spacingpossible (in μm)? c. What is the grating specification (in lines/cm)? What is theminimum width of the grating (in cm)? Please show work! Thanks! . . .