beginfig(16); u:=1.4cm; pickup pencircle scaled 1pt; numeric l,r,t,b; z0=(.3u,5u); t:=y0; l:=x0-.5u; z1=z0+(0,-.3u); z14-z1=whatever*(dir -45); z2=z1+(0,-u); z3-z2=whatever*(dir -45); x3-x2=1u; x4=x3; y4=y3-.4u; z5-z4=whatever*(dir -45); x5=x4+.4u; x14=x5; x6=x5+.4u; y6=y5; z7-z6=whatever*(dir -45); x7=x6+.5u; x8=x7+.4u; y8=y7; z9-z8=whatever*(dir -45); x9-x8=.4u; x10-x9=1.5u; y10=y9; b:=y10-.3u; r:=x10+.5u; x20=x10; y20=b; z15-z10=whatever*(dir -45); x15+.5u=x10; x12+.8u=x15; y12=y15; z13-z12=whatever*(dir -45); y13=y6; draw z0--z1--z2--z3--z4--z5--z6--z7--z8--z9--z10--z15--z12--z13--z6--z5--z14--z1; draw z10--z20; draw (l,t)--(r,t); draw (l,b)--(r,b); x21=x3; y21=y14; x22=x13; y22=y15; x23=x13+.3u; y23=y14+.4u; drawarrow z23--z21; label.lrt(btex $S_i$ etex, z21+(0,-3pt)); drawarrow z23--z22; label.rt("MC regions", z23); z30=whatever[z1,z14]; x30=.3[x1,x14]; z31=whatever[z2,z3]; x31=x30; draw z30--z31 dashed evenly; z32=whatever[z1,z14]; x32=.6[x1,x14]; z33=whatever[z2,z3]; x33=x32; draw z32--z33 dashed evenly; z34=whatever[z1,z14]; x34=.1[x1,x14]; z35=whatever[z2,z3]; x35=x34; draw z34--z35 dashed evenly; pickup pencircle scaled .5pt; drawoptions(withcolor blue); drawdblarrow .6[z34,z35]--.6[z30,z31]; drawdblarrow .4[z30,z31]--.4[z32,z33]; endfig;