Brake away switch wiring to junction box under hitch


I have a 2015 Heartland Big Country 5th Wheel. For whatever reason the Brake Away switch wiring has been pulled loose from the brake away switch and one of the wires pulled out of the junction box. I have purchased a new switch which has two wires that need to be connected in the junction box. Since one of the wires had been pulled completely out of the junction box, I have no idea which wire nut it goes in. I am attaching a picture of the wire groups in the junction box. I have already put one wire from the brake away switch in the "Red & Black" group of wires where you see my hand. The old wire was still attached in this wire nut. Can someone tell me where the other wire attaches.