Question: What Nigerian president appointed the Managing Director of the NPA in 2016?

Context paragraphs:
Bashir Adeniyi Musa: Ambassador Bashir Adeniyi Musa was one of 88 potential ambassadors including nominated by the former Nigerian President Goodluck Jonathan and screened by the Nigerian Senate.  Ambassador Bashir Adenine Musa (Kogi State) was appointed Ambassador to Switzerland, Berne after the senate votes and proceedings on 8 February 2012.  He died on 23 April 2013 after a brief illness.

Andranik Margaryan: Andranik Nahapeti Margaryan (Armenian: Անդրանիկ Նահապետի Մարգարյան , alternative spelling: Andranik Margarian) (12 June 1952 – 25 March 2007) served as the Prime Minister of Armenia from 12 May 2000, when the President appointed him, until his death on 25 March 2007.  He was a member of the Republican Party of Armenia.  He succeeded the Sargsyan brothers: Vazgen Sargsyan, who was murdered during the Armenian parliament shooting on 27 October 1999 and Aram Sargsyan, whom the President appointed a week later, but fired on 2 May 2000.

Mohammed Indimi: Mohammed Indimi is a Nigerian based businessman.  He founded Oriental Energy in 1990, of which he is still chairman.  He is a former in-law of former Nigerian president and retired Nigerian Army general Ibrahim Babangida and a current inlaw to Nigerian president Muhammadu Buhari.

Bill Ernest: William "Bill" Ernest (born December 16, 1950) is the President and Managing Director, Asia, for Walt Disney Parks & Resorts.  He assumed this new role in April 2008.  Ernest was formally the Executive Vice President and Managing Director of Hong Kong Disneyland Resort.  Ernest was named to the position in January 2006, replacing Disney veteran Don Robinson.  Previously, Ernest served as managing director of operations at the Hong Kong resort.

Rilwanu Lukman: Rilwanu Lukman (26 August 1938 – 21 July 2014) was a Nigerian engineer who held several ministerial positions in the Nigerian Federal government before becoming Secretary General of OPEC (Organization of the Petroleum Exporting Countries) from 1 January 1995 to 31 December 2000.  He died on 21 July 2014.  On 18 December 2008, Lukman was appointed Minister of Petroleum Resources by Nigerian president Umaru Yar'Adua, holding office until March 2010.

Muhammadu Buhari: Muhammadu Buhari {'1': ", '2': ", '3': 'GCFR', '4': "} (born 17 December 1942) is the President of Nigeria, in office since 2015.  He is a retired major general in the Nigerian Army and previously served as the nation's head of state from 31 December 1983 to 27 August 1985, after taking power in a military "coup d'état".  The term Buharism is ascribed to the Buhari military government.

National Port Authority: The National Port Authority of the Republic of Liberia ("NPA") is the government agency responsible for the governance and operation of the ports of Liberia.  Established in 1967, its main office is on Bushrod Island in Monrovia and the current Managing Director of the NPA is Hon. Matilda Parker.

Hadiza Bala Usman: Hadiza Bala Usman (born January 2, 1976) is a Nigerian activist and politician.  She is currently the Managing Director of the Nigerian Ports Authority (NPA) as appointed by President Muhammadu Buhari on Monday 11 July 2016.  She was formerly the Chief of Staff for the Kaduna State Governor.  Bala Usman is an active member of the All Progressives Congress (APC).

William J. Mulrow: Bill Mulrow (born January 26, 1956) is an American businessman, investment banker and government official.  He is a Senior Managing Director at the Blackstone Group, an alternative asset manager.  Previously, he was a Director of Global Capital Markets at Citigroup, Inc., a Managing Director of Paladin Capital Group, a Senior Vice President and Head of New Product Development at Gabelli Asset Management (now GAMCO Investors), a Managing Director in Corporate Finance for Rothschild Inc., and a Managing Director and Head of Public Finance Banking for Donaldson, Lufkin and Jenrette Securities Corporation.

Chris Gubbey: Christopher P.M. "Chris" Gubbey (born 11 May 1956 in Gosport, Hampshire, England) is an auto executive, who currently works for General Motors.  Until 2007, Gubbey was the vice president of Shanghai GM.  Gubbey is a graduate of Hatfield Polytechnic and has also held positions at Ford and Toyota.  On 1 July 2007 he officially took up his role as chairman and managing director of Holden, however, after only six months as chairman and managing director, the shortest in the history of the company, Gubbey was replaced by Mark Reuss.  Gubbey has since been appointed GME Vice President and managing director, GM Russia and Commonwealth of Independent States.

Supporting paragraphs: Hadiza Bala Usman Muhammadu Buhari
Answer: Muhammadu Buhari