SMO 2011 Senior Round 1 Question 5

In the figure, $ABC$ is a triangle, and $D,E$ are points on $AB,BC$, respectively. Given $DE\parallel AC$ and $CE:EB=1:3$, the area of $\triangle ABC$ is $1440\text{ cm}^2$ and the area of $\triangle ADE$ is $x\text{ cm}^2$. What is $x$?