.PS
.ps 20
## figure 29
B1:	box invis
	arrow from (B1.sw.x-3*linewid, B1.sw.y-3*lineht) \
	      to (B1.sw.x-4*linewid, B1.sw.y-4*lineht)
B2:	box invis "provider" "rejection" \
		with .ne at (B1.sw.x-4*linewid, B1.sw.y-4*lineht)
##
	line from (B1.nw.x-linewid, B1.n.y+lineht/2) \
	     to   (B1.nw.x-linewid, B2.s.y-lineht/2)
	line from (B2.se.x+linewid, B1.n.y+lineht/2) \
	     to   (B2.se.x+linewid, B2.s.y-lineht/2)
##
.PE