Talk:Research & Development/@comment-217.186.190.34-20151012110354/@comment-26536836-20151018064834

Yes, I think it is extermely hard. I haven't try it much because I'm in 15--I'm not playing for win the car, just for the rewards.

If you can fully pro the car, it was very doable--that's what I heard. And you can play it every 3 hours so sleepless days for playing.

That means you have to spend 3 to 4+ millions credits(not only max upgrade, pro upgrade need credits, too) and so many cards.

And what I've heard, some people are using triple booster to win that ghost ai.