65. What is a firming type in MRP?The firming type determines how procurement proposals are to be firmed and scheduled within the planning time fence during the planning run.Planning time fence: You can protect procurement proposals from any automatic changes to master schedule items in the near future by using the planning time fence. Within the planning time fence, the system does not automatically change procurement proposals during the planning run. That is particularly useful for MPS.Outside of the planning time fence, procurement proposals are created as usual in the planning run. When these procurement proposals move into the planning time fence, they are firmed automatically depending on the setting of the firming type. The system always calculates the end date of the planning time fence dynamically starting from the planning date.