Here's something no one's thought of yet. May sound unlikely, but here goes:
Kisha/Jen & Margie/Luke race for 1st/2nd. Since we are not shown Jaime/Cara checking in, they could be 3rd, but when they get there, Margie/Luke & Kisha/Jen are still arguing. Tammy/Victor are in 4th, but since the fight took so long, they also see the arguing (via pitstop shots). Sound unlikely, but just throwing it out there.