 (a)Wavelength :4680  A 
 Angle of 1st order Diffraction : 28.0 degrees 
 Spacing = 9968.7 A

(b)Wavelength :4800  A 
 Angle of 1st order Diffraction : 28.7 degrees 
 Spacing = 9995.3 A

(c)Wavelength :5770  A 
 Angle of 1st order Diffraction : 35.5 degrees 
 Spacing = 9936.2 A

Mean Spacing = 9966.7 A 