Glen Owns a Building That Is Used in Business

Glen owns a building that is used in business. The building is worth $200,000, but is subject to a mortgage of $40,000. Glen's basis in the building is $120,000. Glen exchanges the building for investment land worth
$150,000 plus $10,000 cash. In addition, the other party assumes the mortgage which will be held for investment. Glen must recognize a gain of

A) $10,000.
B) $80,000.
C) $50,000.
D) $0.