Inventory-dollar-days control measurement (Benchmark)

Determine the appropriate levels for the Customer-Tolerance -Time and Product -Lead-time buffers; if the CTT is longer than the PLT then finished goods inventories held should be nonexistent (or at lest minimal); if CTT is zero, then sufficient finished goods should be held to cover an interval of orders equal to the PLT plus a small Murphy factor; for all other inventory the level  should be held equal to the PLT minus the CTT.