10 points Mark Audio makes wireless headphones. Each pair of headphones comes with a travel case. Mark currently produces 50,000 travel cases annually. Manufacturing costs per case are estimated to be: Direct materials S 10.00 Direct labor S 21.20 Variable overhead S 6.40 S 4.70 $42.30 Fixed overhead Total HTG has offered to sell the case to Mark for $36.00 each. Mark's management will make the switch to HTG cases if Mark can save at least $15,000 per year. Accepting the offer would eliminate allocated annual fixed overhead of $119,000. Estimate Mark's annual savings if it buys the cases from HTG? A positive number should indicate a net savings (from huying) and a negative number a net increase in costs.