You have to get the bag and get it to your base 5 times. When you go to the bag get the powerups in this order: cloak/speed/nothing/cloak/speed. Use your teammates to your advantage. They have one mission in life: Get the bag and protect you when you have the bag.
On all trips to the bag, there's no need to go out of your way to get weapons or health but if you do need health you can get either the vest or the box on the long street. Also on each run to the bag, take the shortcut through the brick building near the beginning.
On the second run, do the same thing as in run #1 but this time get the speed.
On run #3, neither the cloak nor speed will have respawned so you have to go to the bag without either. Blow yourself up again inside the shortcut.
On run #4, the cloak should be available so do the same as in run #1.
On run #5, do the same as in run #2 with the speed but this time run all the way back to your home base. This is why you do the powerups in this order. You want to save the speed for last since you'll be running the entire length and back.