To determine the planned costs for an internally processed activity, you need the duration and activity type data. The duration is the time required to complete the activity. The activity type is a classification of activities according to their functions or characteristics. The system calculates the planned costs for an internally processed activity based on the formula for costing in the work center, the activity output price for the activity type and cost center assigned to the work center, and the duration of the activity. Reference: https://help.sap.com/doc/0f069b2e08b748f1b480d4c8b46c3c49/100/en-US/6a7a9f0a6e421014e10000000a174cb4.html