A sign is seen on the wall outside of a Microsoft store in the Dadeland Mall as Microsoft announces it will be buying Nokia Corp.'s line-up of smart phones on September 3, 2013 in Miami, Florida. The proposed price that Microsoft is paying is reported to be $5 billion for the Nokia unit that makes mobile phones, including its line of Lumia smart phones, and another $2.2 billion will be paid for a 10-year license to use Nokia's patents. (Getty Images)
Vicki Hollub will become the most influential woman in the oil and gas industry when she takes over as CEO of Occidental Petroleum in May. In a bleak period for the sector, how will the future boss of one of America’s biggest energy firms cope with the challenges ahead?