In refining a cost system

$($a$.)$ total direct costs are unchanged because they can be traced in an economically feasible way to the product

and traced costs are more accurate.

b$.$ the costs are grouped in homogeneous pools of the same or similar amounts.

c$.$ the criterion of cause$-$and$-$effect is used to relate indirect costs to a factor that systematically links to a

cost object.

d$.$ the organization looks for cost$-$allocation bases that will provide a uniform spreading of indirect costs to

each product.