Inventory position is 25+15−4=36. A’s reorder point is 8×4+8×2=48; B’s is 8×2+16=32. Forty units cost 40×6+20=260 from A or 40×7+10=290 from B. These are case calculations; a real policy needs measured variability and operational constraints.

Critical check: Do not label the case buffer as a guaranteed service level or treat on-order stock as physically available.

Final project: Build the Birch planning pack: network, inventory definitions, reorder rules, supplier comparison and a late-delivery exception plan.