In 2013, Sierra sold land to her son Jack for $100,000 cash and an installment note for $200,000. Sierra's adjusted basis was $150,000. In 2014, after paying $10,000 interest but nothing on the principal, Jack sold the land for $325,000 cash. As a result of the second disposition, what gain must Sierra recognize in 2014?
a. $200,000.
b. $150,000.
c. $100,000.
d. $50,000.
e. None of the choices.