The men's furnishings buyer received the following data for December 2019: December 2019 Items At cost At retail Opening inventory $4,500 $8,500 New purchase $2,000 $4,000 Net sales $10,000 Markdowns $1,100 Shrinkage $200 Operating expenses $400 Please calculate: a). Cumulative markup% in December 2019 b). Clo inventory at retail in December 2019 c). Closing inventory at cost in December 2019