0 10 20 −4.8 −4.6 −4.4 −4.2 −4 −3.8 (a) 0 10 20 0.1 0.15 0.2 0.25 (b) 0 10 20 0 0.2 0.4 (c) 0 10 20 −0.4 −0.2 0 0.2 0.4 (d) 0 10 20 −0.5 0 0.5 (e) 0 10 20 0.1 0.2 0.3 (f) 0 10 20 −0.5 0 0.5 (g) 0 10 20 −0.5 0 0.5 (h)