APMOPS 2013 Question 13

The diagram shows a parallelogram $ABCD$. $E$ is the midpoint of $AD$. $F$ is the midpoint of $EC$. If the area of the triangle $BFD$ is $9\ \mathrm{cm}^2$, find the area of the parallelogram $ABCD$ in $\mathrm{cm}^2$.