Tom transfers a building that originally cost $40,000 to Paul Corp. in exchange for 100% of the corporation's stock. the adjusted basis of the building is $20,000. at the time of the transfer, the building is subject to a liability of $30,000 (which has no business purpose to it) and it worth $60,000. how much gain must Tom recognize?

a. 0

b. 10,000

c. 30,000

d. 40,000