Milo Contributes a Building with a Fair Market Value of $400,000

Milo contributes a building with a fair market value of $400,000 to a new partnership in exchange for a 25% interest. His adjusted basis in the building is $125,000, which is subject to a $100,000 mortgage. The partnership assumes the mortgage. What is Milo's basis in his partnership interest?

A) $50,000
B) $75,000
C) $100,000
D) $125,000
E) $400,000