Royal Industries Ltd manufacturers plastic lunch boxes in a moulding process. On an annual basis, the industry manufacturers 1,000 plastic lunch boxes at a cost of `4 per unit. The industry’s...

Royal Industries Ltd manufacturers plastic lunch boxes in a moulding process. On an annual basis, the industry manufacturers 1,000 plastic lunch boxes at a cost of `4 per unit. The industry’s differential costs of carrying the item in the finished goods inventory are 20 per cent of the inventory value per year, and the set-up costs per production run is `200. What is the optimum production-run?