The following costs were incurred for Delta Limited to maintain the quality of its products:

a.Repairs to faulty products returned by customers, $12 000

b.Cost of rewelding faulty joints discovered during processing, $3 800

c.Cost of recalling faulty products, $20 000

d.Product inspection into finished goods warehouse, $3 400

e.Cost of faulty goods that were scrapped, $16 800

For the above costs identify the cost category it should belong to?