The volume of the tetrahedron ABCD with vertices A(x1, y1, z1), B(x2, y2, z2), C(x3, y3, z3) and D(x4, y4, z4) is
V = (1/6)|((x1,y1,z1,1),(x2,y2,z2,1),(x3,y3,z3,1),(x4,y4,z4,1))|
The volume of tetrahedron formed by the planes x + y = 0, y + z = 0, z + x = 0 and x + y + z = 1 is
(a) 2/3
(b) 4/3
(c) 8/3
(d) 10/3