Senior Kangaroo 2015 Q7

The diagram shows a triangle $ABC$ with area 12 cm$^2$. The sides of the triangle are extended to points $P$, $Q$, $R$, $S$, $T$ and $U$ as shown so that $PA=AB=BS$, $QA=AC=CT$ and $RB=BC=CU$.

What is the area (in cm$^2$) of hexagon $PQRSTU$?