3 A fruit canning plant has a single line for three different fruit types. Demand for each type of tin is reasonably constant at 50,000 per month (a month has 160 production hours). The tinning process rate is 1,200 per hour, but it takes 2 hours to clean and reset between different runs. The cost of these changeovers (Co) is calculated at £250 per hour. Stock-holding is calculated at £0.1 per tin per month. How big should the batch size be?