u := 1cm;
r := 0.25cm;

beginfig(1);
z1=(0,0);
z4=z1+u*dir0;
z2=z4+u*dir90;
z3=z4+u*dir-90;
z7=z2+2u*dir0;
z5=z4+1.5u*dir0;
z6=z5+1.5u*dir0;
for i=1 upto 7:
	draw  for theta=0 step 10 until 350:  z[i]+r*dir theta..  endfor  cycle;
endfor
drawarrow z1+r*dir45--z2+r*dir-135;
drawarrow z1+r*dir-45--z3+r*dir135;
drawarrow z2+r*dir-90--z4+r*dir90;
drawarrow z3+r*dir90--z4+r*dir-90;
drawarrow z2+r*dir0--z7+r*dir180;
drawarrow z4+r*dir0--z5+r*dir180;
drawarrow z5+r*dir0--z6+r*dir180;
label("3", z1);
label("4", z2);
label("10", z3);
label("6", z4);
label("12", z5);
label("5", z6);
label("9", z7);
label.lft(btex$T_1$etex, z1+r*dir180);
label.top(btex$T_2$etex, z2+r*dir90);
label.bot(btex$T_3$etex, z3+r*dir-90);
label.urt(btex$T_4$etex, z4+r*dir45);
label.bot(btex$T_5$etex, z5+r*dir-90);
label.rt(btex$T_6$etex, z6+r*dir0);
label.rt(btex$T_7$etex, z7+r*dir0);
endfig;

bye