I'm not sure how many vacuum robots I had to banish before the duct tape dropped, but it was a lot! That also meant spending A LOT of oil cans! Doesn't that robot take 5 oil cans each? Little did I know that there would be future quests where I would have to spend 10 & 15 oil cans each to banish different robots. As with everything else in this game, save up when you can.