Dena owns 500 acres of farm land in southeastern Maryland. Her adjusted basis for the land is $480,000 and there is a $400,000 mortgage on the land. She exchanges the land for an office building owned by Chris in Newark, New Jersey. The building has a fair market value of $900,000. What is Dena recognized gain on the exchange?

a) $0

b) $400,000

c) $500,000

d) $820,000