beginfig(1);

u = 50mm;
h = 4mm;
for i = 0 upto 2:
  draw (h + i*u, h)--(h + i*u, 10h);
endfor
drawarrow (0, 2h)--(2h + 2u, 2h);
label.rt("Time", (2h + 2u, 2h));

label.top(btex $t$ etex, (h, 0));
label.bot(btex Period $t+1$ etex, (h + 0.5u, 10h));
label.top(btex $t+1$ etex, (h + 1u, 0));
label.bot(btex Period $t+2$ etex, (h + 1.5u, 10h));
label.top(btex $t+2$ etex, (h + 2u, 0));

draw (h + 0.6u, 2h)--(h + 0.6u, 7h);
label.top("A", (h + 0.6u, h));
drawdblarrow (h + 0.6u, 6.5h)--(h + u, 6.5h);
label.top(btex $T_{margin}$ etex, (h + 0.8u, 6.5h));

draw (h + 0.9u, 2h)--(h + 0.9u, 5h);
label.top("B", (h + 0.9u, h));
draw (h + 1.05u, 2h)--(h + 1.05u, 5h);
label.top("C", (h + 1.05u, h));
drawarrow (0.9u, 4.5h)--(h + 0.9u, 4.5h);
draw (h + 0.9u, 4.5h)--(h + 1.05u, 4.5h);
drawarrow (2h + 1.05u, 4.5h)--(h + 1.05u, 4.5h);
label.rt(btex $T_{response}$ etex, (2h + 1.05u, 4.5h));

endfig;
end