How should i ventilate this room?

Hey RIU, im moving on friday and i have to setup a new room at my new place.

Im gonna setup shop in a walk in closet probably about

15 -20' deep x
8' wide x
8 - 10' high.

I am gonna use the back 1/4 of the closet for a veg area, seperated by black/white poly.

I will have a 400w hps with a bat wing style reflector in the veg area.

In the flowering area i will have a 1000w hps with a vented hood.

I have a 424 cfm 6" inline fan with carbon filter.

Im just not sure how i should exhaust it since i will have it split and sealed and essentially need to exhaust 2 rooms with one fan.

Any ideas?

I would probably just run my ducting directly over each area and in the attic space i would couple the two hoses together with some kind of y-split coupler and just run that into the fan.