N

3

1

5

4

6

2

$T_{cm1}$

$t_a$

$t_b$

$t_c$

$t_c$

$t_b$

$t_a$

$T_{cm2}$

$t_b$

$t_a$

$t_a$

$t_b$

$t_c$

$t_c$

$T_{cm3}$

$t_c$

$t_c$

$t_b$

$t_a$

$t_a$

$t_b$