Stealth Grow box help

I'm building a stealth CFL grow box out of an old dresser running somewhere between 300 and 400 watts of CFL's. I plan on doing a high density SOG flowering from clones. The dimensions are 15"wide by 30"long 32"tall. It is going to be completely sealed so that any air leaving it has to pass through a carbon filter. I need suggestions on fans and how big my vent holes should be to get enough airflow.

There is a formula* for this, i dont know it though.

Anyway, hold out and you will get the correct answer.

fans should be big enuff to clear out the entire room in 5 mins

With my math I get 8.33 cubic feet of volume for the box. Sound about right?

Awww. C'mon people. Do computer fans push enough air to get through some DIY carbon filters? I'm not having much luck finding fairly cheap options.