Mario sold an office building on July 1, 2020, for $180,000. He had purchased the building in 1980 for $150,000 and had properly deducted $108,000 of depreciation, which included $15,500 in additional depreciation. What amount may Mario report as Sec. 1231 gain? A. $42,000 B. $138,000 C. $122,500 D. $15,500