Well look at triangles AEB and CDE. Though they have a vertically opposite angle, they are similar. And using the sides in proportion rule, the ratio of side is 1:3 for AEB:CDE sides. So let AE = x and the DE will be 4-x. Using the ratio of sides, we get:
x/(4-x)=1/3
3x=4-x
4x=4
x=1
So we know the base length of triangle AEC, so we now want the height, which from the diagram we can tell is CD, so 9. Using A=1/2 *b*h we get the area as 4.5, so the answer is D.