Just solder it good, and secure/insulate it with a little electrical tape. Or you can buy some tab connectors and use male connectors crimped onto the cord and pushed under the plastic and against the tab. Again, secure/insulate with some tape. You might want to get some of those wire staples and use them to secure the cords to the rack so they don't get pulled out any more.

Edit: Joe beat me to it. Those tabs suck.