>	diagp:=plot([[t,t+1/12,t=0..11/12],[t,t-1/12,t=1/12..1]],color=[black,black]):

>	boxp:=plot([[t,0,t=0..1],[t,1,t=0..1],[0,t,t=0..1],[1,t,t=0..1]],color=blue):

>	with(plots);

>	display([diagp,boxp],axes=framed,scaling=constrained);

The upper black line here is   and the lower is   The probability that the

two calls come within 5 minutes of each other is the area of the strip between the two lines,

lying within the unit square.