An assignment rule uses its driver formula in a calculation is based on whether the behavior table contains a unit value or a total value.
When a behavior-table row contains a unit value, the driver formula calculates the number of units involved in each transaction that is selected by the selection criteria. Then, the cost per transaction (value) is determined by multiplying the number of units by the unit cost (in the behavior table) of the transaction.
When a behavior-table row contains a total value, the driver formula calculates the number of units involved in each transaction that is picked out by the selection criteria. Then, the cost for that transaction is determined in the following way:
- The total number of units for all transactions (picked out by the selection criteria) is calculated by adding the number of units (as determined by the driver formula) for each transaction (picked out by the selection criteria).
- The cost per unit is calculated by dividing the total value (in the behavior-table row) by the total number of units.
- The cost for each transaction (value) is calculated by multiplying the cost per unit by the number of units (as determined by the driver formula) for that transaction.