The first bakery needs 2 x 4 = <<2*4=8>>8 sacks of strawberries per month.
The second bakery needs 4 x 4 = <<4*4=16>>16 sacks of strawberries per month.
The third bakery needs 12 x 4 = <<12*4=48>>48 sacks of strawberries per month.
Therefore, Antoine needs 48 + 16 + 8 = <<48+16+8=72>>72 sacks of strawberries to supply all the bakeries for a month.
#### 72