There is no direct assignment. You plan the output for a cost center first in kp26. Then you’ve to plan the value of that cost center which you budget for a period in kp06. Planned Activity expenditure / Planned Activity quantity gives you planned act rate which you can use to evaluate your activity confirmations in mfg orders. You can also define your own prices, but you have to run the price revaluation if you want to revaluate your actual activity prices.