marge open an oxygen bar in a building she owns. She used to rent the building to her brother in law for $10,000 a year. To open the oxygen bar, Marge quit her job as a physician assistant, which paid $80,000 a year. As a bar owner, Marge has to pay $40,000 a year wages for the bartender, spend $25,000 a year for supplies, and the utilities billl is $9,500 a year. To cover the start-up costs, she used up all of her savings which earned $4,600 in interest. What are implicit costs?