76. As shown in the figure, in trapezoid $A B C D$, $A D$ is parallel to $B C$, and $B C=2 A D$. Points $E, F$ are the midpoints of $A B$ and $C D$, respectively. It is known that the area of the shaded quadrilateral $E M F N$ is 54 square centimeters. Therefore, the area of trapezoid $A B C D$ is $\qquad$ square centimeters.
Answer: 210