APMOPS 2008 Question 13

Rectangle $ABCD$ has area 32 cm$^2$. Triangle $ADF$ has area 2 cm$^2$ and triangle $ABE$ has area 8 cm$^2$, with $F$ on $DC$ and $E$ on $BC$. The shaded triangle $AEF$ has area $x$ cm$^2$. Find $x$.