Which two questions are typically answered by an inventory model?

An inventory model is fundamentally concerned with the management of inventory levels to optimize operational efficiency and cost-effectiveness. The primary questions addressed by such models focus on timing and quantity related to inventory replenishment.

When determining "when to place an order," an inventory model helps businesses decide the optimal points in time to reorder stock to avoid shortages or overstock situations. This involves analyzing demand patterns, lead times, and carrying costs.

The second aspect, "how many to order," addresses the quantity of inventory to order each time a replenishment is necessary. This is crucial because ordering too much can lead to increased holding costs while ordering too little can result in stockouts and lost sales. Inventory models, such as the Economic Order Quantity (EOQ) model, provide the mathematical foundations to balance these conflicting objectives.

Through these two key aspects—timing and quantity—inventory models aim to maintain sufficient stock levels while minimizing costs associated with ordering and holding inventory. The other options provided focus on aspects like costs, supplier selection, negotiation, and storage management, which, while important in the broader supply chain context, do not directly answer the fundamental questions posed by inventory management models.