[填空题]
A land surveyor is measurifx5vfr 0 x7it n8ddkc-6 du+a2nyhg z 8k*v)smbqo..y 7g the area of a triangular plot of land on a smooth hill. She uses a theodolite to determine the coordinates of the corners of the land and finds them to be (-8,20,10),(16,8,7) and (-20,-8,3) , where the coordi* vg 8yqzm by).h7kso.nates are in metres from a fixed origin where she stands.
Using vectors, determine the area of the land. $m^2$
