Part B (4 Marks) Wang Smelting takes ore and extracts four metals - Zinc, Lead, Copper and Iron - in a joint manufacturing process. The company can sell the metals as is or process them further into a number of different products such as wire or sheeting. Zinc Lead Copper Iron Units produced 10,000 4,000 12,000 20,000 Sales value at split off $20,000 $4,000 $36,000 $10,000 Cost per r unit to process further $1 $0.50 $ 2 $0.50 Per unit sales value if processed $3.25 $1.40 $6 $0.90 Cost of the units up to the split off point are $50,000. Required: Which of the products, if any, should be processed beyond the split-off point? (4 marks)