Which of the following is true of the reciprocal method of cost allocation?

a$.$ This method recognizes all interactions among support departments.

b$.$ In this method, the costs allocated from a support department are only its direct costs.

c$.$ In this method, the costs are allocated in a step$-$down fashion, following a predetermined ranking procedure.

d$.$ This method ignores support department interactions and assigns support department costs only to the producing departments.