People on motor bikes celebrate American President Barack Obama's visit to Kenya by holding up a photo, center top, of the president and First Lady Michelle Obama in Kisumu, Kenya, Saturday, July 25, 2015. President Barack Obama heralded Africa as a continent “on the move” Saturday as he opened a U.S.-sponsored business summit in Kenya, the East African nation where he has deep family ties. (Photo by AP Photo)

The image of President George Washington is seen on an engraving plate for a one dollar bill at the Bureau of Engraving and Printing in Washington November 14, 2014. (Photo by Gary Cameron/Reuters)

The walls of Sydney's Town Hall Station are bedecked to resemble a Woolworths' supermarket shelf in Australia's first virtual supermarket, at Town Hall Station on February 19, 2012 in Sydney, Australia. (Photo by Marianna Massey/Getty Images for Woolworths)

Two Bunny Girls from the Playboy Club and two Penthouse Pets from the Penthouse Club prepare to take part in the annual Good Friday waiters and waitresses race in Battersea Festival Gardens, London, 28th March 1972. (Photo by Ian Showell/Keystone/Hulton Archive/Getty Images)

Competitors line up their boats for some formalities during the Aberdeen Dragon Boat Races. (Photo by Jessica Hromas)

Newly commissioned 2nd lieutenants throw their caps in the air as a team of F-16 Air Force Thunderbirds fly over the 2011 graduating class of the U.S. Air Force Academy on May 25, 2011 in Colorado Springs, Colorado. A total of 1,021 graduates received their diplomas in front of their families and dignitaries at the Academy's Falcon Stadium. (Photo by John Moore/Getty Images)

A protester uses molotov cocktails against riot police during May Day protests on May 1, 2010 in Athens, Greece. (Photo by Milos Bicanski /Getty Images)

In this photo taken Saturday, June 20, 2015, Mahmoud Abdulnabi tries out an oud, an Arabic instrument related to the lute, at his workshop in Baghdad, Iraq. “The oud is different than other musical instruments”, said Abdulnabi, who has crafted ouds played by some of Iraq's best known musicians, many of whom look down from headshots on the walls. “If you feel joyful, it can play your joy. If the circumstances are sad it can play your sorrow and... help to empty whatever is in your chest”. (Photo by Hadi Mizban/AP Photo)