I need help answering this problem

$4\mathrm{.}10$ For the two$-$cell tube shown in

Fig. $4\mathrm{.}18,$ the cell areas are: $A_1=$

$40c{m}^2,A_2=60c{m}^2.$ The wall

lengths are: $L_{12}=13cm,L_{13}=$

$10cm,L_{34}=8cm.$ The wall thick$-$

nesses are: $t_{12}=t_{23}=2mm,t_{13}=$

$1mm,t_{34}=t_{41}=3mm.$ If the

applied torque is $200Nm$ and the

A two$-$cell tube.

modulus of rigidity is $20$GPa, com$-$

pute the shear stresses in the walls and

the rate of twist.