\centerline{
 \beginpicture
 \setcoordinatesystem units <1mm,1mm>
 \setlinear
%
 \setdots <1mm>
 \setlinear
 \plot 0 0  60 20  /
 \put {$\bullet$} at 0 0
 \put {$A_1$} [rt] at -1 0
 \put {$\bullet$} at 60 20
 \put {$E_n$} [lt] at 61 20
 \setquadratic
 \plot 0 0   30 20  60 20 /
 \setlinear
 \plot 30 10  30 16 /
 \put {$\epsilon$} [rb] at 29 11
 \setdots
 \plot 0 6 60 26 /
%
 \endpicture
}