When allocating support departments to producing departments, companies may use "dual charge rates, which are preferred over single charge rates because O dual charge rates recognize that supporting departments have both fixed and variable costs, which should be allocated using separate allocation bases. O dual charge rates recognize that supporting departments have both unit and batch-level costs, which should be allocated using matching causal drivers. O dual charge rates recognize that supporting departments have both indirect and direct costs, which should be allocated or traced as appropriate Odual charge rates recognize that supporting departments have both normal and abnormal costs, which should be assigned to direct cost or overhead respectively.