Won Gold on all Playlist 3 Challenges in Co-op Mode.
Playlist 3 has a total of 3 challenges:

(1) Buenos Aires Speed Check

Gold Medal Requirement: 700.00 MPH (solo) - 1400.00 MPH (co-op)
Preferable Car/s: Dodge Challenger SRT8, Chrysler 300 SRT8 OR Skimmer
Preferable Mods: Double Acceleration - Top Speed - Super Boost

(2) Mexico Survival

Gold Medal Requirement: 05:00:00 min (solo) - 05:00:00 min (co-op)
Preferable Car/s: Dodge Challenger SRT8, Chrysler 300 SRT8 OR Skimmer
Preferable Mods: Double Health - Double Armor - (Explosive Ammo (as a gunman) OR Top Speed (as a driver))

(3) LA Self Destruct

Gold Medal Requirement: 500,000 PTS (solo) - 750,000 PTS (co-op)
Preferable Car/s: Dodge Challenger SRT8, Chrysler 300 SRT8 OR Skimmer
Preferable Mods: Double Health - Top Speed - Double Acceleration