Flaeche des Rechtecks

A = Intersect(n, m)
C = (8, 4)
p = OrthogonalLine(C, m)
q = OrthogonalLine(C, n)
D = Intersect(q, n)
B = Intersect(p, m)
P, a, b, c, d = Polygon(A, B, C, D)