How much ebm for 4 month old?

[AngryGnome]

I know this has probably been asked before but....

I'm leaving my four month old for the day to go on a photography course, and will be out from about 9-5. How much expressed milk will I need to leave for him? I've read somewhere that bf babies need about 25 oz a day on average, so about 1oz per hour, but I'm not sure what age that is for.

Any advice gratefully received!

That's for 1 -6 months (it doesn't change much at all, unlike with FF babies).

Thanks japhrimel, much appreciated!