73. As shown in the figure, in rectangle $A B C D$, $A B=3, B C=2$, points $E$ and $G$ are the midpoints of sides $A D$ and $B C$ respectively, point $F$ is a point on $A B$, and points $E$, $G$, and $H$ are collinear. Find the area of the shaded region.
Reference answer: 3