Please show formula used & work

IP, In preparation for a foreign buying trip, a buyer determines that a 55,40/ markup is required on purchases that will amount to $560,000 at retail While on this trip, the following purchases are made: Cost Retail Resource A $20,000 $45,000 Resource B $50,000 $125,000 Resource C $70,000 $170,000 What markup percentage is needed on the balance of the purchases