[填空题]
A land surveyor is measuring the arsdms 4*w 8 9;surs;n8dsl5bgtea of a trxx uf;:- ly8r,asb,ckiangular 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 coordinates are in metres from a fixed origin where she stanasbfck - ,8u,: lxxr;yds.
Using vectors, determine the area of the land. $m^2$
