in double distribution method, we must allocate just the primary cost of the second allocated department or the primary cost plus the cost received from the other department which allocated before it

that's mean CONSIDER Departement Aand B are supportive DEPARTEMENT and C and D operative department and we start with department A first and allocate it cost then a part of its cost will receiveed by and allocated to the B department .regarding to this step now we must allocate the seconde Departement B which have new cost ( its primary cost and the additional cost which received from department A ) WHAT WE DO for the cost of department B we must allocate its primary cost just or its primary cost plus the cost which received from allocating department A )

i mean department A COST 1000

department B 5000

AFTER allocating department A , department B for example received 700

the next step we must to allocate department B . the question is by which cost the primary cost(5000) or the primary cost plus received one( 5000plus 700)?