Exhaus. Need help

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Hello. I am going to have my first grow and the only thing i need to buy is carbon filter + exhaust fan.I have a sunmaster dual spectrum 400w running in a cool tube. I have a 5" advanced star eco 5" 210m3/h for the cool tube going from outside the tent-duct-cool tube-duct-outside. I bought it for exhust, i was going to suck the air from the tent trough the cool tube in a 50x100x150cm greenhouse but i got 38-40* celsius so i decided to buy a nemesis tent 80x80x180. My question is : what kind of exhaust fan do i need ? I know rvk is good but i m trying to get something cheaper. RAM inline are ok? Any advice is highly apreciated. Thank you. Btw, i will try with 2 autos for my first grow