Two diffraction gratings, A and B, are located at the same distance from the observation screens. Light with the same wavelength ? is used for each. The separation between adjacent principal maxima for grating A is 2.7 cm, and for grating B it is 3.2 cm. Grating A has 1989 lines per meter. How many lines per meter does grating B have? (Hint: The diffraction angles are small enough that the approximation sin(?) ~ tan(?) can be used.)