before 3 shortest 16 first A/B/C [16, 20, None]
before 5 shortest 20 first A/B/C [20, None, 20]
before 6 shortest 20 first A/B/C [None, 24, 20]
before 7 shortest 20 first A/B/C [20, 24, 28]
after 3 shortest 16 first A/B/C [24, 16, None]
after 7 shortest 20 first A/B/C [24, 20, 24]
