a$)$ A retailer forecasts that it will sell $30,000$ units of a product per year. The ordering cost is $$100$ per order, and the holding cost per unit per year is $$2.$ Calculate the Economic Order Quantity $($EOQ$)$ and the number of orders the retailer should place per year to minimise total inventory costs. $(5$ marks$)$ b$)$ Discuss the role of the Economic Order Quantity $($EOQ$)$ model in balancing the costs associated with inventory management and its practical applications.