Nigeria's president-elect Muhammadu Buhari has promised to tackle terrorism and corruption. His pledge comes against a backdrop of vicious attacks by the group Boko Haram and a budget black hole caused by falling oil revenues. General Buhari has already warned that he cannot perform miracles so does he have what it takes to lead Nigeria at one of the most difficult periods in its history? Zeinab Badawi talks to Kayode Fayemi - a key advisor to the president-elect.