Schedule of Activity Costs Quality Control Activities Activity Cost Process audits $48,300 Training of machine operators 28,200 Processing returned products 20,700 Scrap processing (disposal) 24,200 Rework 8,900 Preventative maintenance 29,300 Product design 43,300 Warranty work 10,000 Finished goods inspection 22,800 From the above schedule of activity costs, determine the value-added Oa. $235,700 Ob. $171,900 Oc. $149,100 Od. $181,900