Mark, Nancy, and Carl form a partnership with each partner having an equal share in profits and losses. Mark and Carl each contribute $40,000 in cash to the partnership. Nancy contributes land valued at $100,000. The land has a basis of $90,000 and is encumbered by a $60,000 mortgage that the partnership assumes. What basis does Nancy have in her partnership interest immediately after the contribution of land to the partnership?
a. $50,000
b. $90,000
c. $100,000
d. $110,000