How many?

Mackenzie
go back to work when my lo is 3mo and I'm wandering how many 5oz bottles to buy? Right now he's ebf so I don't know how many he would need for a 12hr period. I have 4 now that I'm using but I also have 7 more that are still in the package I'm thinking of return 4 of them, or maybe exchanging for the 9oz bottles her can use longer.