Question: The Unknown Known, is a 2013 American documentary film about the political career of former U.S. Secretary of Defense and congressman Donald Rumsfeld, an American retired politician and businessman, heserved as the 13th Secretary of Defense from 1975 to 1977 under which President?  
Sentence (from "Donald Rumsfeld"): He is both the youngest and the second oldest person to have served as Secretary of Defense.
Relevant evidence: No