Explanation
When posting an invoice with a cash discount amount using the posting gross method, the cash discount amount is posted to a cash discount clearing account, which is cleared at the time of payment. The posting gross method means that the invoice amount is posted in full to the vendor account and the cash discount clearing account, regardless of whether the payment is made within the cash discount period or not.
References: SAP S/4HANA Sourcing and Procurement | SAP Learning, Course S4515, Unit 3, Lesson 1.

Explanation
A scheduling agreement is a long-term agreement with a vendor for the supply of materials or services according to a predefined delivery schedule. Some features of a scheduling agreement are:
A material master record is optional in a scheduling agreement item. You can use item category M (Material unknown) to enter a short text and material group instead of a material number.
A scheduling agreement can be used for a consignment process. You can use item category K (Consignment) to indicate that the materials are stored at your premises but are still owned by the vendor until you consume them.
A scheduling agreement item is always plant-specific. You must specify a plant for each scheduling agreement item and you cannot change it afterwards. References: SAP S/4HANA Sourcing and Procurement | SAP Learning, Course S4520, Unit 5, Lesson 1.

Explanation
To determine the safety stock during automatic reorder point planning, the system requires the following data:
Service level, which is the probability of avoiding a stockout situation during the replenishment lead time.
Mean absolute deviation, which is a measure of the forecast accuracy based on the historical consumption data.
Replenishment lead time, which is the time required to procure or produce a material. References: SAP S/4HANA Sourcing and Procurement | SAP Learning, Course S4525, Unit 1, Lesson 1.