image dithering on areas of unchanging gray

I have no idea how to accomplish this in Matlab, any clarification would be appreciated..

Show that the 2 × 2 dither matrix D provides appropriate results on areas of unchanging gray. Find the results of D>G when G is a 2 × 2 matrix of values (a) 50, (b) 100, (c) 150, (d) 200.