One of archivements to tower defens is impossible

[TronsGamer]

The archivement say :

I
I calculete the time and money you can get in this 15 minutes without expenses and total money you can expenses is 6500 and for unlock the giant you need spend minimum with zombies 3000 coins.

please solved this problem

 

[TronsGamer]

pd: you can get 5 coins for second

 

[BlueMoon475]

It's not impossible, as someone has already completed this challenge.

https://www.cubecraft.net/threads/true-challenge-not-impossible.97084/

 

[Sophie]

You can kill enemy monsters to receive additional coins. It may take some cooperation between your team mates, however it is possible :)

 

[iLoveYouu]

Aka get some ranked people as your friend and let them give you money..

 

[TronsGamer]

WTF?