P3: (3, 2, 1)
B: (2, 5, 3)
f = Line(P3, B)
P4: (4, 2, 0)
D: (5, 5, 5)
g = Line(P4, D)
d3 = Vector(P3, B)
d4 = Vector(P4, D)
E: (4, 5, 6)
F: (3, 5, 2)
d4sur3 = Vector(P3, E)
d3sur4 = Vector(P4, F)
b = Plane(P3, B, E)
c = Plane(P4, F, D)
P3P4 = Vector(P4, P3)
G: (12, 9, -5)
n = Vector(P3, G)