apportioning costs

hi all,

hope recent results were kind to everyone..

im stuck with a Q on apportionment hope someone could shed some light.

Ive got to allocate temp staff costs and have been given the following info.

DIRECT STAFF COSTS:
PLUMBERS £42300
ELECTRICIANS £15600

INDIRECT STAFF COSTS:
STORES TECHS £22400
CREDIT CONTROL CLERKS £31900

my 3 service centres are industrial repairs, domestic repairs and boiler maintenance repairs

my service centres are stores depart. and general admin

its probably staring me in the face but ive always struggled with costing for some reason, hope it makes sense.

thanks