27. 如图,在四边形ABCDABCDABCD中,∠DAB=120∘\angle DAB=120\circ∠DAB=120∘,∠DAC=30∘\angle DAC=30\circ∠DAC=30∘,AB=1AB=1AB=1,AC=3AC=3AC=3,AD=2AD=2AD=2,AC→=xAB→+yAD→\overrightarrow{AC}=x\overrightarrow{AB}+y\overrightarrow{AD}AC=xAB+yAD,则x+y=(x+y=(x+y=( )))