What is "Economic Order Quantity" $($EOQ$),$ and what does it help to optimize?

a$)$ EOQ is a marketing tool for determining optimal advertising budgets. It helps optimize campaign reach.

b$)$ EOQ is a financial metric for investment decisions. It helps optimize portfolio returns.

c$)$ EOQ is an inventory management formula used to determine the optimal order quantity that minimizes total inventory costs, including ordering and holding costs.

d$)$ EOQ is a quality control measure. It helps optimize product defect rates.