30. As shown in Figure 7, in the hexagon $A B C D E F$, $\angle A=\angle B=\angle C=\angle D=\angle E=\angle F=120^{\circ}, A B=3 \mathrm{~cm}$, $B C=A F=4 \mathrm{~cm}, D C=F E=2 \mathrm{~cm}$. The perimeter of the hexagon $A B C D E F$ is $\qquad$ $\mathrm{cm}$.
Reference answer: 20