The Wizard Emporium specialises in clothing for students attending the local school. Demand is seasonal and care is needed to ensure there is sufficient inventory at the three peak periods of demand. Inventory is expensive but has a long potential shelf-life. Deliveries of orders from the shop's supplier come by train and there are often problems of delays of delivery due to infrequent timetabling of the railway service to the town. Annual sales of school gowns over the past five years have been $420,480,440,520$ and 490 . It costs $£ 80$ to place each order, which must be delivered by hand. Each gown must be stored separately, in a thief-proof storage facility which is rented at a cost of $£ 0.05$ per gown per day.

Required:

(a) Using EOQ, what is the lowest number of gowns that should be ordered so that the costs of purchasing and holding inventory are minimised?

(b) Does this answer appear sensible?