Maryexchanged an office building used in her business for some land. Mary originally purchased the building for $45,000 and it had an adjusted basis of $20,000 at the time of the exchange. The land had a fair market value of $40,000. Mary also gave $4,000 to thein the transaction. What is Mary's adjusted basis in the land after the exchange?

A.$20,000

B. $24,000

C. $36,000

D. $40,000

E. None of the choices are correct