If it's a stake FHC, then I'd think either the FHC would be paying for it out of their budget from the stake or the stake itself would be paying for it. if it's just for the 3 wards, then perhaps an arrangement like with a shared library could be done: the agent unit buys the supplies and bills the other units for their share.
Note, that's it's not uncommon for the FHC to charge for prints and copies to cover the cost of the paper and toner (but not for the FHC budget itself).
Bottom line, this is something the leaders need to work out among themselves. Details of how a FHC should be handled can be found in the
FHC Operations Guide, Finances section.
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