A group of fixtures in a battery vent are vented and have a total of 35 fixture units. If the drain line is 4″ and the battery vent is 45` long, the minimum acceptable size of the battery vent is ____”.

A group of fixtures in a battery vent are vented and have a total of 35 fixture units. If the drain line is 4″ and the battery vent is 45` long, the minimum acceptable size of the battery vent is ____”.