[填空题]
A civil engineer is measuring f0;hfm0iabf/ygp /l- the area of slope3ouzwkiuu2e:zz 0 8ky:b4lp :1apv2 ad land to be used for a residential property development project. She uses a total station theodolite devic:2ui z 4wplkpk 3z2bvy1uaaz 8:ueo:0e to determine the coordinates of the corners of the land and finds them to be (15,25,9),(20,5,5),(-10,-10,2) and (-15,10,6) where the coordinates are in metres from a fixed origin where she is standing. Using vectors, determine the area of the land. $m^2$
