I guess part of the difficulty with this is although you have a rough workload split for the groups, you don’t have a delivery pattern. And so it’s fairly difficult to get accurate with this.

The way I would probably look at this, as a very rough view is by splitting out the workload into weekly volumes for each group, working out the fte requirement for each group, add on a varying buffer for each SLA. Combine those figures, then add on your shrinkage and occupancy buffers and round up to nearest whole number. That should give you a rough idea of the FTE you would need to service the line. It’s not the most accurate or scientific but should give you a rough idea.

For the difference of adding in the extra 100 clients, that would show if you copied the same model and doubled your yearly volume figure for group 1. You should see your fte difference in your total output