=
1 2 1 1
2 4 -1 1
200 200 100 100
1 2 -1 -2
=100
1 2 1 1
2 4 -1 1
2 2 1 1
1 2 -1 -2
=100
1 2 1 1
0 0 -3 -1
0 -2 -1 -1
0 0 -2 -3
=-100
1 2 1 1
0 -2 -1 -1
0 0 -3 -1
0 0 -2 -3
=-100
1 2 1 1
0 -2 -1 -1
0 0 -3 -1
0 0 0 -7/3
=-100X(-2)X(-3)X(-7/3)
=1400