So let’s take 2.6m to allow for dropped ceilings etc that gives you 10.4m need to pump so adds 1.04 bar ontop of your outlet pressure requirement so 4.04 bar required to give you 3 bar 4 floors up
Working on the 70% rule that’s 50 flats needing water at the same time so that’s 1000lpm eg 20lpm...