31. 已知抛物线C:y2=4xC:y^{2}=4xC:y2=4x,过点(0,3)(0,3)(0,3)的直线与CCC交于AAA,BBB两点,线段ABABAB的垂直平分线与xxx轴的交点为点DDD,若AF+BF=6AF+BF=6AF+BF=6,则ΔABD\Delta ABDΔABD的面积为((( )))