A = (0, -6)
B = (2.5, -6)
C = (2.5, 0)
D = (5, 0)
E = (5, 6)
F = (7.5, 6)
G = (7.5, 0)
H = (12, 0)
a = Segment(A, B)
b = Segment(C, D)
c = Segment(E, F)
d = Segment(G, H)