Kai Owns an Apartment Building Held for Investment Purposes

Kai owns an apartment building held for investment purposes. The apartment building is worth $500,000, although it is subject to a mortgage of $100,000. Kai's basis in the apartment building is $380,000. Kai exchanges the apartment building for an office building. The office building has an FMV of $350,000. Kai receives $50,000 cash in addition to receiving the office building, and the other party assumes the apartment building mortgage. What is Kai's recognized gain on this exchange?

A) $0
B) $50,000
C) $150,000
D) $120,000