Vb = Vd = 0 V
Vc = -6 V
Va = -3 V
Vab = -3V
Vbc = 6V
Vab < Vbc
Vac = 3V
Vab < Vac
Vbc > Vac
Vca = -3V
Vba = 3V
Vca < Vba