For comparison, her open PR is 49.59 from 2011.
USA won the race in 3:30.84.
Event 231 Women 4x400 Meter Relay INV C/O
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Team Finals
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Finals
1 Track Master B TC 'A' 3:30.84
1) Kori Carter 2) Allyson Felix
3) Magnolia Howell 4) Carol Rodriguez
2 Brazilian Olympic Comittee 'A' 3:32.22
1) Geisa Coutinho 2) Jailma De Lima
3) Joelma Souza 4) Liliane Fernandes
3 Duke 'A' 3:35.22
1) Lauren Hansson 2) Madeline Kopp
3) Madeline Price 4) Elizabeth Kerpon
FloTrack tweet reporting the split: