Volume of tetrahedron = 1/3 (base area) * height

If the volume of the parallelepiped corresponding to the volume of the tetrahedron is Pv, then the volume of the tetrahedron (Tv) = Pv/6

(x1,y1,z1) is the vertex P

(x2,y2,z2) is the vertex Q

(x3,y3,z3) is the vertex R

(x4,y4,z4) is vertex S.