Courtney sells a cottage at the lake that her family had used for their summer vacations. The purchaser paid Courtney $100,000 and assumed the mortgage which had a principal balance of $50,000. Courtney had purchased the cottage five years ago for $170,000. Courtney will recognize A. a gain of $20,000 B. a loss of $70,000 C. a loss of $20,000 D.no gain or loss