Read this and answer the question. If the question is unanswerable, say "unanswerable".

Northwestern is privately owned and is governed by an appointed Board of Trustees. The board, composed of 70 members and as of 2011[update] chaired by William A. Osborn '69, delegates its power to an elected president to serve as the chief executive officer of the university. Northwestern has had sixteen presidents in its history (excluding interim presidents), the current president, Morton O. Schapiro, an economist, having succeeded Henry Bienen whose 14-year tenure ended on August 31, 2009. The president has a staff of vice presidents, directors, and other assistants for administrative, financial, faculty, and student matters. Daniel I. Linzer, provost since September 2007, serves under the president as the chief academic officer of the university to whom the deans of every academic school, leaders of cross-disciplinary units, and chairs of the standing faculty committee report.

How many members are on Northwestern's Board of Trustees?
70